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can the amount of muscle and fat that
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you have in your body change your
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appetite and what happens if you lose
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weight let's talk about that
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how's it going guys my name is richie
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kirwan and today we're going to talk
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about some of the ways that your body
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regulates its appetite and the important
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role that your muscle body fat and even
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bone have in keeping you from getting
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hungry lots of people have tried to lose
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weight at some point in their lives and
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unfortunately some have tried and failed
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many times it's really easy to assume
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that they might have been following the
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wrong diet or even worse to think that
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they weren't disciplined enough but the
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trying to lose weight is a battle
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against one of the most powerful
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adversaries we'll ever face
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our own brains you see your brain is
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wired through billions of years of
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evolution to seek out food no matter how
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much you might want to get ready for
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bikini season i've spoken about some of
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the reasons in my video on why losing
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weight is so hard so remember to check
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that out after this video and if you're
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really interested you could check out
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the book the hungry brain by stefan
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giene which goes into incredible detail
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on how our brain makes eating less a lot
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harder especially in the modern world
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with 24 7 access to delicious calorie
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dense food the fact that there are whole
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books written on this means that
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appetite control is a really complex
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topic that i couldn't hope to cover in
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just one video but instead i'm going to
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talk about how changes in your level of
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muscle mass and body fat can cause
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changes in your appetite that might make
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dieting a whole lot harder we'll also
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talk about how even your bones might
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have a whole role to play themselves in
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controlling how much you eat first off
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let's talk about body fat and the
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concept of the lipostat lipo comes from
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the greek word for fat and stat as in
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the word thermostat something that helps
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us to maintain a constant state so body
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fat produces a hormone called leptin
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and more body fat you have generally the
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more leptin you produce in healthy
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people leptin actually causes us to eat
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it does this by affecting the
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hypothalamus the part of the brain that
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helps to control appetite when leptin
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was first discovered there was actually
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a lot of excitement about it because
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people thought it might be possible to
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control appetite just by injecting
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people with leptin unfortunately
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experiments trying to do just that never
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actually worked out in humans but you
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might ask what about people with a lot
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of body fat why doesn't leptin stop them
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from eating too much that's one of the
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reasons appetite control is so complex
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we know that in people with obesity they
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have very high levels of leptin but they
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also suffer from something called leptin
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resistance this means their bodies have
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been exposed to high levels of leptin
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for so long that they've lost their
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sensitivity to it it's kind of similar
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to how people become insulin resistant
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and don't react to insulin in the same
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way on the other hand if people lose a
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lot of body fat or even if they just
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drop calories for a while leptin levels
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can drop and this causes appetite to
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increase and we want to eat more we also
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know that you can temporarily increase
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leptin by eating more especially by
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eating carbohydrates but it's a very
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short-lived increase so it doesn't
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really help someone who's trying a
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longer term low calorie diet or trying
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to maintain weight loss another possible
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way our body can regulate our body
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weight strangely enough might be through
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our bones so i want to talk about one of
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the best research studies i've read in
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the past few years the only problem with
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it is that it was done in mice which
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might make you think that it doesn't
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apply to humans but we'll talk about
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that in a minute so in the original
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experiment some researchers in sweden
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surgically implanted tiny weights into
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some mice to artificially make them
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heavier over the course of about two
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weeks the mice with the added weight
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from their body fat compared to mice
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that didn't have any weights at it that
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was an interesting fighting by itself so
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the researchers wanted to find out why
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it happened through a few different
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experiments they found out that the mice
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with added weights were eating less and
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they also found out that the reason they
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were eating less had nothing to do with
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leptin but that wasn't enough for the
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researchers so they did even more
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experiments and found out that the
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weight loss effect didn't happen in mice
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that were missing a specific type of
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bone cell called osteocytes the
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researchers came up with the idea that
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the osteocytes in the mice's leg bones
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were able to detect changes in body
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weight this means that when the
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scientists added the weights to mice the
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bone cells detected the extra weight and
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sent a signal to the mouse's brain
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basically saying hey we feel we're too
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heavy right now time to eat a little
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less and get the weight down the
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research team call this weight control
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system the gravitostat because of the
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force of gravity is helping to control
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body weight what's interesting is that
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in the modern world a lot of people
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spend most of their life sitting down
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which means bone cells in their legs
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don't get much opportunity to detect
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their body weight and might not be able
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to help them regulate appetite all that
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well however that's a very early theory
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at the moment and needs more evidence so
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the scientists decided to try and see if
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they could do something similar in
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humans what they did is they got a group
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of participants with obesity to walk
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around with weighted vests that were
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about 11 percent of their body weight
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which means 100 kilogram person would
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wear an 11 kilogram vest for eight hours
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a day for three weeks what they found is
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that the participants in the weighted
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vests lost more body weight and body fat
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but not muscle mass compared to a
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control group with no weighted vests the
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researchers think but don't know just
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yet that this weight loss may be due to
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reduce appetite and not you to burning
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more energy just walking around with the
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added weight now these are just a couple
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of experiments but it gives you an idea
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of how animal research can be used to
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design human research and give us an
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idea of another way our bodies are able
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to regulate our body weight finally
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there's another way that our body might
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control our appetite through how much
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muscle we have there's no official name
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for this so i'm calling it the sarcostat
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from the greek word sarc meaning flesh
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or muscle so think of it like this when
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people lose weight they often lose a
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combination of body fat and muscle mass
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unless they do plenty of resistance
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exercise to hold on to it we've already
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mentioned that the loss of body fat
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leads to a drop in leptin that can
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increase appetite well it turns out that
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the loss of muscle mass might have the
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same effect when our level of muscle
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mass shrinks we can see a change in
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certain hormones that are produced in
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our muscles firstly the amount of
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ghrelin produced in our muscles goes up
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ghrelin is a hormone that acts on the
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hypothalamus in the brain to stimulate
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appetite and make us eat more secondly
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less muscle can lead to a decrease in a
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protein messenger called myostatin
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myosin is a pretty well known molecule
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because it actually stops muscle growth
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and genetic mutants that don't produce
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myostatin are known to have huge muscles
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just google myostatin mutant bull or
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you'll see some incredible photos so
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when myostatin goes down another
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molecule called insulin-like growth
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factor goes up and this also affects the
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hypothalamus in the brain increases
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appetite and causes us to eat more the
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possible reason for this is that our
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body is trying to maintain our muscle
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mass and when it detects a sudden drop
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in muscle mass it makes us eat more so
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that we can put on some weight and
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hopefully regain that loss muscle the
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drop in myostatin would help with this
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extra muscle gain too could this mean
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that having more muscle is a good idea
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to reduce appetite we honestly don't
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know because we need a lot more research
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to figure that out so there you have
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three possible ways that different
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tissues in our body our fat our bones
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and our muscle can affect our appetite
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and cause changes in our body weight
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like i said earlier there really are
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many more ways that our body regulates
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appetite and how much we eat and they're
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all incredibly complex with more
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research we'll probably discover even
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more systems of appetite control so what
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i know that was a more sciency
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theoretical kind of look at appetite but
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i hope you found it interesting as
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always if you have any questions let me
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know in the comments below and remember
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to like and subscribe to the my protein
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youtube channel for more great
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evidence-based nutrition information
