1 00:00:04,450 --> 00:00:07,450 Jen: Welcome to the So That's Why podcast, where we unpack the 2 00:00:07,450 --> 00:00:09,290 science behind everyday questions. 3 00:00:09,320 --> 00:00:09,910 I'm Jen. 4 00:00:10,250 --> 00:00:10,780 Matt: I'm Chris. 5 00:00:11,510 --> 00:00:12,320 And I'm Matt. 6 00:00:12,980 --> 00:00:13,340 Jen: Okay. 7 00:00:13,400 --> 00:00:18,160 I'm sure loads of listeners can relate to today's topic, especially if you 8 00:00:18,170 --> 00:00:22,949 have ever uttered the words, "My metabolism has definitely slowed down." 9 00:00:23,490 --> 00:00:26,779 So why does our metabolism slow with age? 10 00:00:27,210 --> 00:00:30,210 Matt: Well, I am definitely one of the people that says, "My 11 00:00:30,210 --> 00:00:34,280 metabolism has slowed down." It's one of my favorite things to say. 12 00:00:34,280 --> 00:00:36,599 It's a great excuse I've found as I'm getting older. 13 00:00:36,720 --> 00:00:37,370 Jen: Definitely. 14 00:00:38,110 --> 00:00:41,670 Chris: Well, there's a rather large piece of research with 15 00:00:41,670 --> 00:00:42,800 an awkward answer for you, I'm 16 00:00:42,800 --> 00:00:43,089 Matt: afraid. 17 00:00:43,089 --> 00:00:43,689 I'm not interested. 18 00:00:43,820 --> 00:00:45,219 Let's end the podcast right now. 19 00:00:45,559 --> 00:00:49,310 Jen: And normally we'd make everyone wait, but this one works 20 00:00:49,310 --> 00:00:50,830 better the other way around. 21 00:00:50,839 --> 00:00:51,819 So Chris, hit us. 22 00:00:52,780 --> 00:00:52,980 Chris: Yeah, 23 00:00:53,159 --> 00:00:53,369 Jen: so 24 00:00:54,089 --> 00:00:58,460 Chris: for the fact fans, um, for most of our adult life, metabolism 25 00:00:58,469 --> 00:01:02,030 doesn't actually sh- slow down at all, despite what we all naturally think. 26 00:01:02,390 --> 00:01:07,940 So between the age of 20 and 60, metabolic rate is essentially flat. 27 00:01:08,460 --> 00:01:11,899 Matt: Flat, as in nothing happens. 28 00:01:12,659 --> 00:01:15,180 I mean, to be fair, like I said, I've been blaming my metabolic rate for 29 00:01:15,180 --> 00:01:16,630 a fair, fair number of years now. 30 00:01:16,659 --> 00:01:20,000 Jen: Yeah, and you've been blaming an innocent party, so it's like accusing 31 00:01:20,000 --> 00:01:23,570 a housemate who moved out years ago of finishing all the biscuits. 32 00:01:23,610 --> 00:01:25,849 Matt: They did finish- … the biscuits. 33 00:01:26,380 --> 00:01:27,520 I'm convinced of it. 34 00:01:27,859 --> 00:01:32,850 Anyway, so, uh, I guess then, am I the suspect? 35 00:01:32,850 --> 00:01:36,189 Is it me, half nine at night with the fridge door open, you know, with the 36 00:01:36,190 --> 00:01:37,770 excuse, "Well, it's been a bit of a day"? 37 00:01:38,649 --> 00:01:41,119 Chris: Uh, before I continue, just for the record, I'd like it 38 00:01:41,119 --> 00:01:44,130 noted, I had nothing to do with the disappearance of your biscuits. 39 00:01:44,330 --> 00:01:44,999 Did I, Matt? 40 00:01:46,379 --> 00:01:46,949 Jen: Noted. 41 00:01:47,179 --> 00:01:47,709 Okay. 42 00:01:48,649 --> 00:01:52,719 So let's get into this properly because the story is far better than the myth. 43 00:01:53,530 --> 00:01:58,220 Chris: So in this study, the test is called, um, doubly labeled water, and 44 00:01:58,240 --> 00:02:02,410 it's the gold standard for measuring total energy expenditure in real life. 45 00:02:02,750 --> 00:02:05,670 And the reason it's called doubly labeled water is because the water 46 00:02:05,670 --> 00:02:11,090 itself contains heavy forms of hydrogen and oxygen, which are then tracked or 47 00:02:11,090 --> 00:02:16,210 labeled, and the rate those isotopes leave your body tells the researchers 48 00:02:16,230 --> 00:02:20,550 how much CO2 you're producing, and therefore how much energy you're burning 49 00:02:21,120 --> 00:02:24,210 Jen: And crucially, it isn't a treadmill test. 50 00:02:24,220 --> 00:02:28,990 It's real life over days, including the bits when you're asleep or 51 00:02:29,040 --> 00:02:32,410 arguing about who's turned the thermostat up or down in your house. 52 00:02:32,410 --> 00:02:33,550 Do you ever have that in your house? 53 00:02:33,550 --> 00:02:33,680 Yeah, 54 00:02:33,720 --> 00:02:33,930 Matt: no. 55 00:02:33,930 --> 00:02:36,030 Jen: You 56 00:02:36,030 --> 00:02:37,780 Chris: know, we've got one person on the graph for turn it up 57 00:02:38,700 --> 00:02:39,190 Jen: and one of us- Yeah, 58 00:02:39,190 --> 00:02:39,560 Chris: yeah 59 00:02:39,560 --> 00:02:39,695 … Jen: for 60 00:02:39,695 --> 00:02:40,100 Matt: turn it down. 61 00:02:40,100 --> 00:02:41,590 I just have a mobile app, I win every time. 62 00:02:42,910 --> 00:02:45,970 Chris: Yeah, and on this study, they, um, they actually did it on over 6,000 63 00:02:46,000 --> 00:02:52,030 people, and they're aged from eight days old all the way to 95 years old, um, 64 00:02:52,050 --> 00:02:54,040 across, I think it was 29 countries. 65 00:02:54,629 --> 00:02:57,130 Let's be honest, that's quite a decent cross-section of the population, isn't it? 66 00:02:57,140 --> 00:02:59,120 Jen: Yeah, it's quite robust, that study, isn't it? 67 00:02:59,379 --> 00:02:59,730 Matt: It is. 68 00:02:59,730 --> 00:03:02,290 I wanna know who had the conversation with the parent of 69 00:03:02,290 --> 00:03:03,980 an eight ye- eight-day-old baby. 70 00:03:04,190 --> 00:03:04,819 "Do you mind?" 71 00:03:04,980 --> 00:03:05,499 Jen: I know. 72 00:03:05,600 --> 00:03:08,580 And they were actually in the right head space to make a decision to say yeah. 73 00:03:08,820 --> 00:03:11,850 Chris: I know, and as it happens, I mean, the, the baby turns out to be the 74 00:03:11,850 --> 00:03:13,480 most impressive person in this study. 75 00:03:13,690 --> 00:03:16,250 And I don't mean because they were kind of mature enough to actually 76 00:03:16,250 --> 00:03:18,470 sign off their own consent. 77 00:03:18,470 --> 00:03:23,750 Um, energy expenditure peaks at around eight or nine months old, when babies 78 00:03:23,750 --> 00:03:28,590 are burning roughly 50% faster than an adult, kind of relative to body size. 79 00:03:29,120 --> 00:03:29,920 Matt: 50%. 80 00:03:29,949 --> 00:03:33,749 They can't even hold their own head up properly, and they 81 00:03:33,750 --> 00:03:35,359 seem to be out metabolizing me. 82 00:03:35,540 --> 00:03:35,950 Jen: Yeah. 83 00:03:35,980 --> 00:03:39,150 Well, it's the building, which is, that's the most expensive 84 00:03:39,150 --> 00:03:40,600 thing that the body ever does. 85 00:03:40,629 --> 00:03:46,560 But you know, after that, it declines through childhood and adolescence, and 86 00:03:46,560 --> 00:03:49,380 then settles around, like, the age of 20. 87 00:03:50,759 --> 00:03:51,050 Chris: I know. 88 00:03:51,119 --> 00:03:54,199 And then from 20 to 60, basically nothing. 89 00:03:54,830 --> 00:03:57,679 No dip in the 30s, no crash in the 40s. 90 00:03:58,160 --> 00:04:01,109 There's no measurable effect of menopause or pregnancy either once 91 00:04:01,110 --> 00:04:03,329 you account for size and composition. 92 00:04:03,339 --> 00:04:03,359 So- 93 00:04:03,770 --> 00:04:05,630 Jen: People will not wanna hear this, will they? 94 00:04:05,630 --> 00:04:06,360 Matt: Yeah, no, I know. 95 00:04:07,030 --> 00:04:07,290 No. 96 00:04:07,830 --> 00:04:11,979 And what does accounting for size and composition actually mean? 97 00:04:12,409 --> 00:04:13,989 Chris: That sounds like you're questioning the study there, but- 98 00:04:14,049 --> 00:04:14,609 Matt: I, I- 99 00:04:14,799 --> 00:04:15,310 Jen: This was a robust 100 00:04:15,310 --> 00:04:15,339 Chris: study. 101 00:04:15,339 --> 00:04:15,369 Yeah. 102 00:04:15,369 --> 00:04:17,800 Matt's trying to find holes. 103 00:04:19,319 --> 00:04:23,369 Um, in the study, they corrected for how much of you there is and how much 104 00:04:23,369 --> 00:04:25,619 of that is muscle rather than fat. 105 00:04:26,249 --> 00:04:29,479 And basically, a bigger body burns more in total. 106 00:04:29,539 --> 00:04:32,729 So without that correction, you're just measuring size. 107 00:04:33,169 --> 00:04:36,329 Jen: And once you correct for it, so the rate per kilo of tissue, it 108 00:04:36,329 --> 00:04:38,749 remains steady across the four decades. 109 00:04:38,759 --> 00:04:42,199 So your machinery isn't getting worse with age. 110 00:04:42,239 --> 00:04:46,309 There may simply be less of the expensive machinery in your body. 111 00:04:46,799 --> 00:04:50,049 Matt: And those are two completely different problems though, aren't they? 112 00:04:50,049 --> 00:04:54,509 One is your body failing, the other maybe is your body composition changing. 113 00:04:54,519 --> 00:04:54,839 Jen: Mm. 114 00:04:54,919 --> 00:04:57,769 Chris: Yep, and of course, only one of those is a fair description of 115 00:04:57,769 --> 00:04:59,439 what actually happens in midlife. 116 00:04:59,909 --> 00:05:03,399 Jen: Which brings us to the awkward question, if the rate 117 00:05:03,459 --> 00:05:08,599 is flat, why do so many people gain weight in that exact window? 118 00:05:08,989 --> 00:05:12,119 Matt: And I'd like to state for the record that I know the 119 00:05:12,119 --> 00:05:15,239 answer, I just don't care for it. 120 00:05:16,419 --> 00:05:19,469 Chris: Well, in that case, I'll say it gently and- … diplomatically. 121 00:05:19,909 --> 00:05:22,549 It's about, let's call it energy balance. 122 00:05:22,559 --> 00:05:26,319 So you get more energy going in than going out, and of course, this is 123 00:05:26,329 --> 00:05:29,349 sustained over years rather than weeks. 124 00:05:29,909 --> 00:05:34,059 Jen: So there's a professor of nutrition at King's College London called Tom 125 00:05:34,059 --> 00:05:38,939 Sanders, and he said, "Findings like these support the view that rise in 126 00:05:38,939 --> 00:05:45,949 obesity is driven by excess energy intake rather than falling energy expenditure." 127 00:05:46,339 --> 00:05:50,659 Matt: And the thing there is that nobody makes that decision once. 128 00:05:50,729 --> 00:05:51,019 Jen: Mm. 129 00:05:51,029 --> 00:05:54,819 Matt: It's a few hundred small decisions that I guess we're 130 00:05:54,819 --> 00:05:56,029 just not keeping score of. 131 00:05:56,691 --> 00:05:56,961 Jen: No. 132 00:05:57,711 --> 00:06:01,171 And I'd rather people heard that as good news, because everything 133 00:06:01,171 --> 00:06:05,281 that is the problem is something you can actually influence. 134 00:06:05,871 --> 00:06:10,671 Your muscle mass, how much you move, and sadly, what's on your plate. 135 00:06:10,831 --> 00:06:10,851 Yeah. 136 00:06:11,661 --> 00:06:12,301 Matt: Which is- Or what's in your plate … what you said. 137 00:06:13,561 --> 00:06:14,221 Mm-hmm, yeah. 138 00:06:14,791 --> 00:06:18,311 Well, yeah, I, I guess I could look at it as like it's oddly freeing, right? 139 00:06:18,321 --> 00:06:22,221 Mm. I generally file this under the things that happen to you, you know, a bit like 140 00:06:22,521 --> 00:06:26,161 gray hair and your knees sort of making that noise when you climb the stairs. 141 00:06:26,551 --> 00:06:27,401 Chris: I thought that was just me. 142 00:06:29,241 --> 00:06:29,871 That, that, that grating noise. 143 00:06:29,871 --> 00:06:30,801 Where is that noise coming from? 144 00:06:30,811 --> 00:06:30,911 Yeah. 145 00:06:31,851 --> 00:06:35,281 Uh, but after 60, something actually does change, and that same 146 00:06:35,281 --> 00:06:37,501 study is very clear about this. 147 00:06:38,031 --> 00:06:42,601 Matt: Yeah, so there's a real decline, and it just happens about 30 years 148 00:06:42,601 --> 00:06:44,181 later than we actually think it does. 149 00:06:44,181 --> 00:06:45,521 Well, certainly the internet does anyway. 150 00:06:45,531 --> 00:06:50,061 Jen: Yeah, and that decline is only about 0.7% a year. 151 00:06:50,371 --> 00:06:53,291 It's tiny, but it adds up. 152 00:06:53,291 --> 00:06:57,601 So by the age of 90, your total energy expenditure is around 153 00:06:58,561 --> 00:07:01,031 26% lower than in mid-life. 154 00:07:01,531 --> 00:07:04,171 Matt: And 26% is not nothing. 155 00:07:04,411 --> 00:07:05,631 Chris: No, it's substantial. 156 00:07:05,751 --> 00:07:09,911 And, um, the mechanisms are where this gets good, and there are four 157 00:07:09,951 --> 00:07:12,151 things all happening at once here. 158 00:07:12,521 --> 00:07:16,141 Jen: Okay, so start with the big one, because it's also the one 159 00:07:16,141 --> 00:07:17,691 people have most control over. 160 00:07:18,181 --> 00:07:22,921 Chris: Yeah, so it's what's known as sarcopenia, and this is, um, age-related 161 00:07:23,121 --> 00:07:25,331 loss of skeletal muscle mass and strength. 162 00:07:25,681 --> 00:07:31,671 So inactive adults can lose 3 to 5% of their muscle per decade from their 30s, 163 00:07:32,371 --> 00:07:34,011 and that accelerates through your 40s. 164 00:07:34,501 --> 00:07:37,221 Matt: Yeah, so the muscle starts going long before the 165 00:07:37,231 --> 00:07:39,301 metabolic rate drops or goes. 166 00:07:39,621 --> 00:07:43,981 Jen: Yeah, and that matters because muscle is metabolically active tissue, 167 00:07:43,981 --> 00:07:48,741 so it costs energy to maintain, even when you're sitting completely still 168 00:07:49,643 --> 00:07:50,463 Chris: Yeah, absolutely. 169 00:07:50,503 --> 00:07:55,893 And, um, there was a, a systemic review of resting metabolic rate in older adults, 170 00:07:56,383 --> 00:08:01,633 and it, uh, it found the drop was m- predicted far more strongly by muscle 171 00:08:01,633 --> 00:08:06,043 mass loss than by total body weight or anything else about body composition. 172 00:08:06,043 --> 00:08:09,213 So in all those studies, muscle was the main player. 173 00:08:09,963 --> 00:08:14,023 Matt: So keeping muscle isn't really just a gym thing then, it's also about how 174 00:08:14,023 --> 00:08:17,313 much energy your body burns while resting. 175 00:08:17,403 --> 00:08:21,093 Jen: Yeah, so think of it like, um, the standing charge on your energy bill. 176 00:08:21,353 --> 00:08:26,343 Muscle is the bit you pay for whether or not you switch any energy on in the house. 177 00:08:26,523 --> 00:08:27,363 Matt: The standing charge. 178 00:08:27,403 --> 00:08:28,483 I like that analogy. 179 00:08:28,483 --> 00:08:31,593 So lifting weights then can make a huge difference as you get older. 180 00:08:31,793 --> 00:08:32,003 Jen: Mm. 181 00:08:32,253 --> 00:08:34,233 Chris: Yeah, and it's not always the, as I say, it's not always just about 182 00:08:34,233 --> 00:08:35,393 the gym, it can be little things. 183 00:08:35,393 --> 00:08:39,253 So lifting those bags of groceries on the weekly shop, it counts as something. 184 00:08:39,453 --> 00:08:41,193 It's not much, but it's at least something. 185 00:08:41,193 --> 00:08:41,463 Better than nothing. 186 00:08:41,463 --> 00:08:42,893 Matt: You keep telling yourself 187 00:08:44,133 --> 00:08:44,163 Chris: that. 188 00:08:45,663 --> 00:08:45,733 You don't see 189 00:08:45,733 --> 00:08:45,916 Jen: the bags I've got to carry home. 190 00:08:45,916 --> 00:08:48,583 Well, it depends what's in your shopping bags really. 191 00:08:50,133 --> 00:08:54,413 Okay, so the second mechanism, and this is one you can't lift your way out 192 00:08:54,413 --> 00:08:57,443 of, is the mitochondria in your body. 193 00:08:57,683 --> 00:08:59,383 Matt: The powerhouse of the cell. 194 00:09:00,543 --> 00:09:03,683 Chris: You were listening at, uh, secondary school- Yeah … biology. 195 00:09:04,413 --> 00:09:05,373 Uh, but that's the one, yeah. 196 00:09:05,413 --> 00:09:08,213 And, um, it's, it's a fair description as far as it goes, 197 00:09:08,213 --> 00:09:09,093 the kind of, what did you say? 198 00:09:09,153 --> 00:09:09,853 The powerhouse- The 199 00:09:09,853 --> 00:09:11,743 Matt: powerhouse of the cell. 200 00:09:11,923 --> 00:09:12,663 Chris: I won't say it in that typical tone. 201 00:09:12,663 --> 00:09:12,963 I was gonna say, 202 00:09:13,293 --> 00:09:14,383 Jen: you have to say it in that voice. 203 00:09:16,563 --> 00:09:17,303 Chris: Um, where were we? 204 00:09:17,303 --> 00:09:17,753 Yeah, the mitochondria. 205 00:09:18,133 --> 00:09:23,783 So the my- the mitochondria generates ATP, or adenosine triphosphate, which is the 206 00:09:23,853 --> 00:09:26,343 actual energy currency your cells spend. 207 00:09:26,873 --> 00:09:31,033 Jen: But over a lifetime, the mitochondrial DNA, they get mu- it can get 208 00:09:31,033 --> 00:09:37,433 mutations and oxidative damage, so they start to make the ATP less efficiently. 209 00:09:37,703 --> 00:09:41,023 And sadly, that is one of the core hallmarks of aging. 210 00:09:41,433 --> 00:09:44,373 Chris: It is, and just to add to that, of course, the quality control process 211 00:09:44,373 --> 00:09:48,593 that clears damaged mitochondria, which is called mi- mitophagy, uh, that 212 00:09:48,593 --> 00:09:50,473 itself becomes less effective with age. 213 00:09:50,483 --> 00:09:53,933 So the faulty ones accumulate and the problem compounds. 214 00:09:54,193 --> 00:09:57,693 Matt: So it's wear and tear, plus the, I guess the maintenance 215 00:09:57,693 --> 00:09:59,143 team that's also slowing down. 216 00:09:59,443 --> 00:10:03,693 Jen: Yeah, and it hits the hardest in the tissues with the highest 217 00:10:03,703 --> 00:10:07,963 energy demand, like your muscles, your heart, liver, your brain. 218 00:10:08,633 --> 00:10:09,133 Chris: That's right. 219 00:10:09,133 --> 00:10:11,503 And then we, we're onto the third, which is, uh, hormones. 220 00:10:11,513 --> 00:10:16,913 So the growth hormone, uh, IGF-1, and testosterone, they all decline 221 00:10:17,003 --> 00:10:20,803 alongside changes in thyroid function and insulin sensitivity. 222 00:10:21,123 --> 00:10:24,953 So these are all signals that tell your body to build tissue. 223 00:10:25,553 --> 00:10:28,463 Jen: So the building materials still arrive, the instruction to 224 00:10:28,463 --> 00:10:29,483 use them is just a little bit quiet. 225 00:10:31,019 --> 00:10:32,779 Matt: Dun, dun. 226 00:10:32,779 --> 00:10:34,169 Okay, this is great news, this. 227 00:10:34,359 --> 00:10:35,239 What's the fourth one? 228 00:10:35,779 --> 00:10:38,009 Chris: Well, I wanna test you on one to three f- first to see if you 229 00:10:38,369 --> 00:10:38,499 Matt: have retention. 230 00:10:38,569 --> 00:10:39,369 Okay, so muscles- 231 00:10:39,539 --> 00:10:39,819 Jen: Yeah 232 00:10:41,289 --> 00:10:42,059 Matt: ATP- M- … mitochondria Mitochondria, 233 00:10:42,139 --> 00:10:42,399 Jen: yeah 234 00:10:42,569 --> 00:10:43,649 … Matt: uh, hormones. 235 00:10:43,989 --> 00:10:44,879 Jen: Well done. 236 00:10:45,379 --> 00:10:45,859 Chris: Wow. 237 00:10:45,889 --> 00:10:46,979 I, I, yeah. 238 00:10:48,779 --> 00:10:49,059 There you go. 239 00:10:49,119 --> 00:10:50,589 Matt: Hey, never studied, whatever. 240 00:10:50,589 --> 00:10:50,609 In 241 00:10:50,979 --> 00:10:52,109 Chris: that case, we'll go on to the fourth. 242 00:10:52,819 --> 00:10:55,389 Um, and this is actually the one that I, I find the most striking. 243 00:10:55,389 --> 00:11:00,109 So after 60, that energy expenditure falls by more than you can explain 244 00:11:00,109 --> 00:11:02,529 by just muscle loss and fat alone. 245 00:11:02,999 --> 00:11:06,969 Jen: Which means the tissues that, that's left is doing less per kilo. 246 00:11:06,969 --> 00:11:10,359 So it isn't just that there's less of you working, the cells 247 00:11:10,359 --> 00:11:12,529 themselves are running slower. 248 00:11:13,039 --> 00:11:15,979 Matt: So using your machinery, there's less machinery. 249 00:11:16,459 --> 00:11:20,459 Uh, but after 60, I guess the machinery changes too? 250 00:11:21,009 --> 00:11:23,559 Jen: Then there's one more piece, 'cause there always is. 251 00:11:24,479 --> 00:11:27,579 Um, it's why- Inevitably … the practical advice looks the way it 252 00:11:27,589 --> 00:11:30,179 does, and that is anabolic resistance. 253 00:11:30,479 --> 00:11:32,869 Matt: Which sounds like something a fitness app would charge 254 00:11:32,869 --> 00:11:34,069 you a monthly amount for. 255 00:11:34,399 --> 00:11:34,899 Jen: Yeah. 256 00:11:34,949 --> 00:11:37,589 Chris: Yeah, but anabolic resistance also sounds like the, the force 257 00:11:37,609 --> 00:11:38,839 that we need to fight the AI robots. 258 00:11:40,679 --> 00:11:42,729 Release the anabolic 259 00:11:42,729 --> 00:11:44,299 Matt: resistance. 260 00:11:44,299 --> 00:11:47,849 You can tell me what's calling right now, the anabolic resistance movie. 261 00:11:48,229 --> 00:11:48,309 Yeah. 262 00:11:48,649 --> 00:11:49,079 Chris: Absolutely. 263 00:11:49,079 --> 00:11:52,619 And, um, anabolic resistance, it- its role is kind of, it's simpler 264 00:11:52,619 --> 00:11:54,029 than the name might suggest. 265 00:11:54,109 --> 00:11:58,179 So, um, aging muscle responds less strongly to the two things 266 00:11:58,179 --> 00:12:02,109 that normally trigger it to build, eating protein and using the muscle 267 00:12:02,993 --> 00:12:07,653 Jen: And given, a given amount of dietary protein produces a smaller 268 00:12:07,833 --> 00:12:12,193 muscle-building response in an older adult than a younger one, so you need 269 00:12:12,193 --> 00:12:14,593 a bigger nudge for the same effect. 270 00:12:14,783 --> 00:12:16,013 Matt: I've been married 28 years. 271 00:12:16,013 --> 00:12:19,033 My wife will agree, you need a bigger nudge for the same effect. 272 00:12:22,293 --> 00:12:24,303 So it hasn't just stopped working. 273 00:12:24,523 --> 00:12:27,163 I guess, in my language, the volume just needs turning up. 274 00:12:27,283 --> 00:12:27,673 Jen: Mm. 275 00:12:27,733 --> 00:12:31,053 Chris: That's right, and, um, when that doesn't happen, you can end up with 276 00:12:31,053 --> 00:12:36,093 what research called sarcopenic obesity, where the muscle loss and fat gain happen 277 00:12:36,093 --> 00:12:37,823 together, hence why we need this, like- 278 00:12:37,993 --> 00:12:38,263 Matt: Mm 279 00:12:38,403 --> 00:12:39,463 … Chris: anabolic resistance. 280 00:12:41,013 --> 00:12:41,583 Matt: Dun, dun, dun. 281 00:12:41,583 --> 00:12:42,333 We really do. 282 00:12:43,603 --> 00:12:48,783 Jen: And so when you, you know, gain fat and muscle together, this carries 283 00:12:48,803 --> 00:12:53,153 a higher rate of metabolic disorder and a higher mortality risk than either 284 00:12:53,153 --> 00:12:58,043 alone, and it's self-reinforcing because less muscle means less strength, less 285 00:12:58,043 --> 00:13:00,763 activity, which costs you more muscle. 286 00:13:01,143 --> 00:13:04,693 Matt: Yeah, and that's a loop that only runs one way, unfortunately, unless, 287 00:13:04,693 --> 00:13:06,773 I guess you interrupt it somehow. 288 00:13:07,123 --> 00:13:11,643 Jen: Okay, so let's talk about what does interrupt it, starting with the strongest, 289 00:13:11,643 --> 00:13:14,243 which isn't a supplement or a diet. 290 00:13:14,693 --> 00:13:16,453 Chris: That's it, and we've mentioned it a few times now. 291 00:13:16,463 --> 00:13:19,903 It's about resistance, and specifically resistance training. 292 00:13:20,223 --> 00:13:24,353 So this is the, the kind of single most evidence-backed intervention because 293 00:13:24,703 --> 00:13:28,943 it targets the biggest modifiable driver here, which is muscle loss. 294 00:13:29,413 --> 00:13:33,833 Matt: So is there then an age where it stops being worth starting? 295 00:13:33,943 --> 00:13:35,983 So if you're listening to the show and you're like, "I don't 296 00:13:35,993 --> 00:13:39,443 do weights or any resistance training, am I too old to start?" 297 00:13:40,033 --> 00:13:43,123 Jen: No, and that's actually the most encouraging part. 298 00:13:43,143 --> 00:13:48,163 So your muscle protein synthesis machi- machi- meh- … machinery 299 00:13:49,421 --> 00:13:54,771 It stays responsive to a training stimulus up to, like, very old age. 300 00:13:55,101 --> 00:13:58,351 Chris: That's right, and studies show it improves the efficiency of everyday 301 00:13:58,451 --> 00:14:03,331 movement in older adults, and preserves or builds lean mass well into later life. 302 00:14:03,331 --> 00:14:06,021 So, I mean, we joked about kind of picking up heavy bags 303 00:14:06,021 --> 00:14:08,031 of groceries, but this counts. 304 00:14:08,081 --> 00:14:08,931 Jen: There's truth in it. 305 00:14:08,931 --> 00:14:10,951 Chris: So I think the, the bottom line is don't stop. 306 00:14:11,041 --> 00:14:13,371 If you can pick things up, don't stop- Yeah 307 00:14:13,511 --> 00:14:13,839 … Matt: regardless of your age. 308 00:14:13,839 --> 00:14:13,973 Yeah, yeah. 309 00:14:13,973 --> 00:14:14,174 It all helps. 310 00:14:14,174 --> 00:14:15,591 Start if you haven't done so already. 311 00:14:15,931 --> 00:14:16,221 Jen: Yeah. 312 00:14:17,081 --> 00:14:20,831 Okay, so there's weights, and then there's protein to consider, and this 313 00:14:20,971 --> 00:14:22,071 is where the numbers have changed. 314 00:14:22,071 --> 00:14:27,031 So the recommended daily allowance of, like, 0.8 grams per kilo of 315 00:14:27,031 --> 00:14:32,681 body weight a day is now widely considered too low for older adults. 316 00:14:33,061 --> 00:14:35,641 Chris: It is, and these recommendations are always changing, aren't they? 317 00:14:35,641 --> 00:14:42,021 But at time of recording, it's currently sitting at- Yeah … about 1 to 1.2 grams 318 00:14:42,361 --> 00:14:48,531 per kilogram of body weight as standard, and 1.2 to 1.5 grams per kilogram of 319 00:14:48,531 --> 00:14:50,791 weight if you're training as well. 320 00:14:50,931 --> 00:14:51,301 Yeah. 321 00:14:51,301 --> 00:14:53,461 Maybe more if you're training heavily, like, you know, like me. 322 00:14:53,861 --> 00:14:54,821 Matt: Like, obviously, like, yeah. 323 00:14:54,821 --> 00:14:56,741 I'm just, I- I thought you were on two to two and a half grams of protein. 324 00:14:56,751 --> 00:14:57,111 Yeah. 325 00:14:57,311 --> 00:14:57,391 Chris: Yeah. 326 00:14:58,081 --> 00:15:01,981 Matt: Uh, but, yeah, I guess doing some quick maths, if you're around 70 kilos, 327 00:15:02,291 --> 00:15:04,701 that's about 80 or 90 grams a day. 328 00:15:04,881 --> 00:15:10,101 Jen: Yeah, roughly, and the per meal matter, number matters just as much 329 00:15:10,111 --> 00:15:16,051 because maximal protein synthesis in older adults takes around 25 to 40 grams 330 00:15:16,051 --> 00:15:21,871 of a good quality protein in a sitting, against about 20 in younger adults. 331 00:15:21,901 --> 00:15:25,331 Chris: Mm. Yeah, and something else worth keeping in mind is, um, the option 332 00:15:25,331 --> 00:15:28,871 of spreading it evenly across three meals, which stimulates more muscle 333 00:15:28,871 --> 00:15:33,771 protein synthesis over a kind of 24-hour period than loading it all at once. 334 00:15:33,851 --> 00:15:35,921 Mm. Which does go against the, the way a lot of people do, do it, doesn't it? 335 00:15:35,921 --> 00:15:36,501 Jen: Yeah. 336 00:15:36,911 --> 00:15:40,771 Matt: Yeah, it does, because I guess most of us, I don't know, we toast something 337 00:15:40,771 --> 00:15:44,351 beige at lunch, and then have the enormous protein-shaped dinner of an evening. 338 00:15:44,471 --> 00:15:47,151 Jen: I'm feeling quite self-righteous at the moment, 'cause I do 339 00:15:47,171 --> 00:15:48,931 have a good protein breakfast. 340 00:15:48,961 --> 00:15:52,491 Matt: Okay, Jen, you do know, right, there's no protein in a cup of tea? 341 00:15:52,491 --> 00:15:53,765 I just wanna point 342 00:15:53,765 --> 00:15:54,401 Jen: that out. 343 00:15:54,401 --> 00:15:59,671 Chris: I can see the product development team behind Matt saying- … protein 344 00:15:59,671 --> 00:15:59,741 tea, yep, get it on the list. 345 00:16:01,139 --> 00:16:03,609 I don't wanna be the one that does the lab trials on the protein tea 346 00:16:03,629 --> 00:16:04,229 Matt: Yeah, no, that 347 00:16:04,229 --> 00:16:04,565 Chris: would be nasty 348 00:16:04,565 --> 00:16:05,514 this is not gonna be very pleasant, is it? 349 00:16:05,514 --> 00:16:05,619 Yeah, 350 00:16:05,619 --> 00:16:05,639 Jen: yeah. 351 00:16:05,669 --> 00:16:06,229 No. 352 00:16:06,669 --> 00:16:07,629 Chris: That's a big teabag as well. 353 00:16:07,639 --> 00:16:07,659 Yeah. 354 00:16:10,139 --> 00:16:12,949 Um, Captain Sensible moment, I'm afraid. 355 00:16:13,019 --> 00:16:13,579 Dun, dun, dun. 356 00:16:13,579 --> 00:16:15,989 I think it's the first one of this episode, so I haven't been too bad. 357 00:16:15,989 --> 00:16:17,689 Jen: Yeah, people have been waiting for it, I'm sure. 358 00:16:17,689 --> 00:16:18,129 Chris: I know, yeah. 359 00:16:18,129 --> 00:16:21,139 I need a, I want, like, a lanyard or a, a actual cap. 360 00:16:21,299 --> 00:16:21,469 Jen: Yeah. 361 00:16:21,469 --> 00:16:21,549 I think you 362 00:16:21,549 --> 00:16:22,669 Matt: should get, like, a cape. 363 00:16:23,059 --> 00:16:23,799 Chris: Yes. 364 00:16:25,039 --> 00:16:27,249 Not all, not all Captain Sensibles wear capes. 365 00:16:27,799 --> 00:16:28,139 Not 366 00:16:28,139 --> 00:16:28,529 Jen: capes. 367 00:16:28,529 --> 00:16:29,709 No, but maybe just a cap. 368 00:16:31,229 --> 00:16:31,979 Chris: Um, I forgot what the 369 00:16:33,889 --> 00:16:34,194 Jen: Captain Sensible bit was. 370 00:16:34,194 --> 00:16:34,499 About kidneys, maybe? 371 00:16:34,949 --> 00:16:35,019 Chris: Yes. 372 00:16:35,049 --> 00:16:36,579 On a serious note, well, thank you. 373 00:16:37,329 --> 00:16:37,819 You remembered. 374 00:16:37,819 --> 00:16:42,509 Um, if you've got a kidney disease or if you're on a restricted diet for 375 00:16:42,509 --> 00:16:46,369 medical reasons, protein targets are really a conversation for your doctor 376 00:16:46,639 --> 00:16:50,839 because they're so individual, you can do a lot of damage by just going 377 00:16:50,839 --> 00:16:52,499 with generic numbers thrown about- Mm 378 00:16:52,499 --> 00:16:52,959 the internet. 379 00:16:52,959 --> 00:16:55,089 So just something to keep in mind and be careful of. 380 00:16:55,589 --> 00:16:56,409 Jen: Thank you, Captain. 381 00:16:56,949 --> 00:17:01,959 Okay, let's chat about creatine, because that has had so much, and is still 382 00:17:01,959 --> 00:17:03,819 getting so much, of attention, isn't it? 383 00:17:04,249 --> 00:17:05,939 Chris: It is, and I think rightly, too. 384 00:17:06,119 --> 00:17:12,369 And, um, there was a 2025 systematic review and meta-analysis of kind of papers 385 00:17:12,389 --> 00:17:18,539 and publications, and it found that, um, creatine plus resistance training improved 386 00:17:18,539 --> 00:17:23,229 lower limb strength and lean muscle mass far more than just training alone. 387 00:17:23,949 --> 00:17:26,749 Matt: More than training alone is an important phrase, because 388 00:17:26,759 --> 00:17:29,719 creatine is not a, a replacement. 389 00:17:29,719 --> 00:17:30,649 It is an addition. 390 00:17:30,889 --> 00:17:31,309 Jen: Yeah. 391 00:17:31,449 --> 00:17:35,509 And the effects, um, in those trials, they were seeing the most, you know, 392 00:17:35,509 --> 00:17:40,109 the most visible effects were in the first 32 weeks, and it actually looked 393 00:17:40,139 --> 00:17:44,259 the same across, you know, men and women and different fitness levels as well. 394 00:17:44,329 --> 00:17:44,539 Matt: Mm. 395 00:17:44,989 --> 00:17:45,309 Chris: Yeah. 396 00:17:45,309 --> 00:17:49,389 And, um, although evidence in people over 90 who are still fairly is, is 397 00:17:49,389 --> 00:17:53,869 genuinely limited, it's a, it's a gap worth noting, but it's, this is 398 00:17:53,869 --> 00:17:55,509 not an unmeasured benefit, is it? 399 00:17:55,519 --> 00:17:56,999 So we've seen this across groups. 400 00:17:57,179 --> 00:17:59,639 It's fair to say there aren't that many people over 90 maybe who go to 401 00:17:59,639 --> 00:18:04,359 the gym who the, the studies were able to target, but I think creatine as a 402 00:18:04,359 --> 00:18:05,479 whole is really interesting, isn't it? 403 00:18:05,519 --> 00:18:05,769 And- 404 00:18:05,799 --> 00:18:06,299 Jen: Mm. 405 00:18:06,299 --> 00:18:09,349 Chris: Mm … I think for the, the elderly, there's a lot more to go 406 00:18:09,349 --> 00:18:10,869 in terms of studies on creatine. 407 00:18:10,869 --> 00:18:10,959 So 408 00:18:10,959 --> 00:18:11,529 Jen: watch this space. 409 00:18:11,539 --> 00:18:11,719 Chris: Yeah. 410 00:18:11,719 --> 00:18:12,589 Jen: Vegetology 411 00:18:12,589 --> 00:18:14,479 Matt: creatine, coming soon. 412 00:18:15,339 --> 00:18:16,489 Chris: Yeah, the, oh, the product development team, they're ready. 413 00:18:16,529 --> 00:18:19,549 The, the whiteboard over Matt's shoulder's now- 414 00:18:19,739 --> 00:18:20,229 Matt: Yeah … the board. 415 00:18:20,229 --> 00:18:21,529 Team creatine. 416 00:18:21,549 --> 00:18:22,679 Maybe we could do it all together 417 00:18:24,231 --> 00:18:24,921 Jen: That would taste… 418 00:18:24,921 --> 00:18:25,421 No, that wouldn't taste good. 419 00:18:27,631 --> 00:18:27,961 Okay. 420 00:18:27,961 --> 00:18:31,311 So moving on from creatine, let's talk about aerobic activity. 421 00:18:31,541 --> 00:18:38,271 So that burns, obviously, energy directly, and also supports your cardiovascular 422 00:18:38,271 --> 00:18:44,001 health, um, but is beneficial alongside strength work, um, like weightlifting. 423 00:18:44,001 --> 00:18:49,171 So I think the recommended is at least 150 minutes a week. 424 00:18:49,521 --> 00:18:52,701 Matt: Yeah, and that doesn't have to be, like, a formal exercise, 425 00:18:52,701 --> 00:18:53,841 like, you know, like on a treadmill. 426 00:18:53,861 --> 00:18:54,361 Jen: No. 427 00:18:54,401 --> 00:18:55,071 Chris: No, that's right. 428 00:18:55,071 --> 00:18:58,651 So walking, uh, cycling, swimming, they all count. 429 00:18:59,091 --> 00:19:02,191 Um, and so does the kind of low-level activity that we talked about earlier 430 00:19:02,191 --> 00:19:05,031 that you do without even thinking about, be it the, the picking up the shops, uh, 431 00:19:05,501 --> 00:19:07,171 the shopping- Yeah, picking up the shops 432 00:19:07,611 --> 00:19:07,781 sorry, the groceries. 433 00:19:09,121 --> 00:19:09,141 Jen: Yeah. 434 00:19:09,141 --> 00:19:12,511 Tell you what, if you can manage that at the age of 90, Guinness Book of Records. 435 00:19:13,051 --> 00:19:13,211 Chris: Yeah. 436 00:19:13,211 --> 00:19:15,411 No creatine required if you, if you can do that. 437 00:19:15,771 --> 00:19:18,171 Uh, but those things, they add up way more than people kind 438 00:19:18,171 --> 00:19:19,401 of maybe expect or assume. 439 00:19:20,391 --> 00:19:22,931 Jen: So we've covered some of the more obvious things, but then there's 440 00:19:22,931 --> 00:19:27,841 the easy things that people, well, usually ask about that, um, to help 441 00:19:27,851 --> 00:19:32,591 boo- boost metabolism, like caffeine, which is the obvious one, and green 442 00:19:32,591 --> 00:19:35,901 tea is another one, probably due to its antioxidant properties. 443 00:19:36,391 --> 00:19:37,811 Matt: Go on then, break my heart. 444 00:19:37,821 --> 00:19:38,141 Come on. 445 00:19:38,341 --> 00:19:39,701 Give me the lowdown on caffeine. 446 00:19:40,191 --> 00:19:42,701 Chris: Well, there is a measurable effect 447 00:19:44,731 --> 00:19:44,841 of caffeine. 448 00:19:44,841 --> 00:19:44,861 Woo! 449 00:19:44,861 --> 00:19:48,751 That's the good news, because studies have shown that, um, it- 450 00:19:48,911 --> 00:19:53,251 caffeine does transiently increase energy expenditure and fat oxidation 451 00:19:53,291 --> 00:19:55,041 under sedentary conditions. 452 00:19:55,051 --> 00:19:56,741 So if you- Wow. 453 00:19:56,741 --> 00:19:57,131 Right … sit around, it's doing a job. 454 00:19:57,191 --> 00:19:57,691 Matt: Yeah, yeah. 455 00:19:58,031 --> 00:19:58,061 Jen: But… 456 00:19:58,961 --> 00:19:59,791 Chris: There's always a but. 457 00:20:00,121 --> 00:20:01,201 I didn't do the but this time. 458 00:20:01,201 --> 00:20:01,461 Yeah. 459 00:20:03,071 --> 00:20:05,231 It's normally Prince of Darkness over here who does the but 460 00:20:07,547 --> 00:20:11,427 Jen: But the effect sizes are small and they are quite short-lived 461 00:20:11,447 --> 00:20:14,067 and they're nowhere near the league of like building muscle. 462 00:20:14,067 --> 00:20:16,807 So they're real, but they're quite modest. 463 00:20:17,007 --> 00:20:17,287 Chris: Yeah. 464 00:20:17,287 --> 00:20:21,727 So they are a nice little temporary thing, but they're not exactly a strategy, you 465 00:20:21,727 --> 00:20:23,557 know, being just caffeine or green tea. 466 00:20:23,667 --> 00:20:23,947 Matt: Mm. 467 00:20:24,357 --> 00:20:25,067 Chris: Do you like green tea? 468 00:20:25,067 --> 00:20:25,207 No. 469 00:20:25,207 --> 00:20:26,377 I, I've got into green tea. 470 00:20:26,567 --> 00:20:27,207 I've… Yeah, I drink it. 471 00:20:27,507 --> 00:20:29,597 Matt: No, I just, I just prefer normal tea. 472 00:20:29,617 --> 00:20:31,217 Jen: I feel like it's something you tolerate. 473 00:20:31,787 --> 00:20:31,977 Matt: Yeah. 474 00:20:32,597 --> 00:20:34,467 Yeah, I've just not built up the resistance for 475 00:20:34,477 --> 00:20:34,497 Chris: it. 476 00:20:34,507 --> 00:20:36,267 Actually, I have to drink decaffeinated green tea, 'cause it- 477 00:20:37,557 --> 00:20:38,297 Jen: Rock and roll. 478 00:20:38,297 --> 00:20:42,357 Matt: So, so you're definitely not gonna benefit from this study then are you? 479 00:20:43,117 --> 00:20:46,077 Chris: No, but luckily green tea's full of antioxidants, which are, are good. 480 00:20:46,117 --> 00:20:47,107 Ah, okay. 481 00:20:47,107 --> 00:20:48,287 They, they do the same thing, so it's the kind of healthier version. 482 00:20:48,287 --> 00:20:48,347 He'll be 483 00:20:48,347 --> 00:20:49,517 Jen: laughing when he's 90. 484 00:20:49,757 --> 00:20:51,087 Matt: Yeah, yeah, yeah. 485 00:20:51,087 --> 00:20:53,497 Metabolic rate- Yeah … still faster than the speed of sound. 486 00:20:53,647 --> 00:20:58,057 Chris: No joy, 'cause I'm just drinking- … bitter green tea, but there you go. 487 00:20:59,207 --> 00:21:03,087 Um, but here's something else that surprises people, and another one 488 00:21:03,117 --> 00:21:08,217 potentially for the fact fans out there, that cutting calories hard doesn't raise 489 00:21:08,247 --> 00:21:10,337 metabolic rate as a lot of people believe. 490 00:21:10,377 --> 00:21:15,067 Mm. So more, um, calorie restriction generally lowers energy expenditure. 491 00:21:16,177 --> 00:21:16,527 Matt: Yeah. 492 00:21:16,527 --> 00:21:19,777 It is, I think, a little bit opposite to what everyone hopes for, isn't it? 493 00:21:19,777 --> 00:21:22,767 When they cut calorie diets, they hope, uh, cut their calories, it, they 494 00:21:22,767 --> 00:21:23,957 hope that it's gonna increase their- 495 00:21:24,047 --> 00:21:24,327 Jen: Yeah, 496 00:21:24,327 --> 00:21:24,947 Matt: yeah … metabolic 497 00:21:24,947 --> 00:21:24,977 Jen: rate. 498 00:21:24,977 --> 00:21:25,967 Yeah, it is. 499 00:21:26,397 --> 00:21:30,607 Um, calorie restriction, it can improve how your mitochondria work, 500 00:21:30,677 --> 00:21:35,487 at least in lab studies, but that's, that's about keeping cells healthy. 501 00:21:35,487 --> 00:21:39,817 It doesn't necessarily mean you're burning more calories day to day. 502 00:21:40,397 --> 00:21:40,697 Matt: Yeah. 503 00:21:40,697 --> 00:21:45,337 So for the metabolic rate specifically, the heavi- heaviest evidence then sort 504 00:21:45,337 --> 00:21:50,217 of sits with training and protein rather than supplements or your green tea. 505 00:21:50,377 --> 00:21:50,717 Jen: Yeah. 506 00:21:50,727 --> 00:21:51,427 Chris: I think that's fair. 507 00:21:51,477 --> 00:21:54,717 Um, let- let's say with the potential addition of creatine, because 508 00:21:54,987 --> 00:21:56,317 that is a well-supported extra. 509 00:21:56,367 --> 00:21:56,647 Jen: Mm. 510 00:21:57,097 --> 00:22:01,247 Chris: Um, but it's, it's worth keeping in mind that the, the gains are incremental. 511 00:22:01,697 --> 00:22:04,067 Uh, they're not things that are just gonna happen overnight, so you've, 512 00:22:04,067 --> 00:22:08,517 you've gotta kinda bear with these pro- kind of processes or dietary choices. 513 00:22:08,637 --> 00:22:09,137 Jen: Yeah. 514 00:22:09,697 --> 00:22:10,137 Okay. 515 00:22:10,287 --> 00:22:14,287 So why does our metabolism slow with age? 516 00:22:14,837 --> 00:22:20,107 Chris: So after 60, when it genuinely does slow by just under 1% a year, 517 00:22:21,067 --> 00:22:24,967 muscle loss drives this slowing down, but so too does mitochondria, which 518 00:22:24,977 --> 00:22:31,177 is making less ATP efficiently, uh, by anabolic hormones falling away and by 519 00:22:31,197 --> 00:22:35,317 the tissue that's left doing less per kilogram of body weight than it used to. 520 00:22:36,227 --> 00:22:40,337 Matt: And before 60, it mostly doesn't, which means the thing that 521 00:22:40,337 --> 00:22:45,287 I've been muttering about since I was in my mid-30s, well, it's kinda 522 00:22:45,287 --> 00:22:46,997 got a solid alibi, hasn't it, really? 523 00:22:47,117 --> 00:22:48,547 Jen: Yes, a very solid one. 524 00:22:48,607 --> 00:22:52,277 6,400 people, 29 countries, case dismissed. 525 00:22:53,027 --> 00:22:53,467 Matt: All right. 526 00:22:53,477 --> 00:22:55,007 All right, numbers girl over there. 527 00:22:55,347 --> 00:22:58,917 I've been blaming a complete bystander, I suppose, for 10 years. 528 00:22:59,647 --> 00:23:02,917 Chris: Yep, and it's fair to say the, um, the practical version's very short. 529 00:23:03,417 --> 00:23:05,647 Keep the muscle you've got and feed it properly. 530 00:23:06,147 --> 00:23:09,557 Your body stays responsive to training and diet far longer, far 531 00:23:09,557 --> 00:23:11,017 longer into life than people assume. 532 00:23:12,087 --> 00:23:13,787 Jen: So that's it for this week. 533 00:23:13,867 --> 00:23:16,157 Make sure you hit that subscribe button. 534 00:23:16,347 --> 00:23:19,447 We're gonna keep unpacking the science behind everyday questions. 535 00:23:19,447 --> 00:23:22,857 Tell us in the comments what you'd like us to explore next. 536 00:23:23,277 --> 00:23:26,317 Thanks for geeking out with us, but for now, that's it from me. 537 00:23:26,687 --> 00:23:27,497 Matt: That's it from me. 538 00:23:27,837 --> 00:23:28,827 Chris: And that's it from me. 539 00:23:28,987 --> 00:23:29,687 Jen: Bye for now.