The Biochemistry of Weight Loss

Just cam across this on YouTube, and found it interesting. Considering how many times questions around weight loss arise on the forum (not least posted by me!), it might be something to factor into our discussions.

that was good, cheers.

Good chat but honestly not sure what his point is beyond the bromide of eat less / move more?

Yes I saw that some time ago. I think what he was getting at is that weight loss is basically down to what you exhale. So yes, it’s a simple mass in/mass out equation.

He mentioned hormones in passing though, but said nothing about levels of those hormones or what affects them or any of it.

It is still more complicated than he suggests.

At heart, I know you’re right, @molgrips. But he turned the air in a balloon to liquid. He could have told me that trees were stone at that point and I would have believed him.

I’m not entirely convinced by the simple (simplistic?) calories in/calories out equation. The body excretes excess vitamins and nutrients, it feels like an oversimplification to suggest that it could not do the same with energy, to a certain extent. We have all known scrawny people who put away tones of shit food, and we’ve probably all experienced middle age spread where it becomes increasingly hard work to keep the waistline under control despite increased activity and greater awareness of of dietary do’s and don’ts. I’m not trying to find excuses for McDonald’s mainlining land whales, but I think there definitely IS a genetic element to who stores excess calories, as well as where they store them.

v8ninety

I think you are basically right. Here is my take on it

Calorie in out is 100% true no exceptions (except maybe surgery)

But

That doesn’t tell us how it feels and it doesn’t take into account how our bodies respond

Drink a sugary drink, get an insulin spike, low blood sugar and feel hungry. That doesn’t undermine calories in out but reminds us that some calories makes us feel different. Reduced calories can reduce our calorie consumption.

The skinny guy who eat loads burns more calories. Genetics might mean that he burns them sat completely still

It is all about energy in vs. energy out. Your body cannot create energy from nothing and it takes an energy investment for your body to create body fat. The biggest problem is people often underestimate their calorie consumption and overestimate their calorie output. Or they do some exercise and immediately consume a high calorie drink or food to ‘reward’ themselves completely undoing all their good work. It’s not rocket science and even properly fat people who cannot lose weight then go and get a gastric band on the NHS lose weight…not because of metabolism or those mythical ‘hormones’, but because they’ve had their food intake drastically reduced. It’s pretty simple really. There is no easy way around it…if you want to lose weight you have to spend part of the day hungry.

It depends how fast your metabolism runs. If you’ve got a fast metabolism and you’re naturally slim you can eat more and ride less than someone who has a slow metabolism and you’ll still be thinner than them. Also I think if you eat lots of the right things fruits vegetables etc after a ride instead of high fat and sugar foods you’ll see more advantages (this is the calories in calories out part). It wasn’t until I started monitoring my calories burned on rides and looking at food labels that I realised how difficult it is to burn more than you eat. A chocolate hobnob is 94 calories, I burn 500 on a 20km ride. So all I need do to tip the balance is eat 6 chocolate hobnobs and I’ve already negated a 20k ride. Obviously a heavier rider burns more calories in that distance but can probably put away more biscuits

It is all about energy in vs. energy out

It’s really not – because if that were true then everyone who over-ate would get fat, and we know that doesn’t happen.

Calories you eat don’t automatically end up converted to fat. There are (afaik) a number of hormones that trigger that process. And if you eat fewer calories than you use, a number of things have to happen for your body to convert fat into energy and the efficiency of that process depends on a load of things.

There is no easy way around it…if you want to lose weight you have to spend part of the day hungry.

The thing your brain registers as ‘hunger’ is a manifold set of signals, and your brain can be tricked. So this is also not true.

Just because you think human metabolism is simple, doesn’t mean it is! In general yes eating less and moving more is strongly correlated with having less weight, but there are many exceptions to that and if you change your eating habits or exercise you don’t automatically lose or gain weight.

There are also feedback mechanisms that work to maintain your weight the same. If there weren’t, everyone who didn’t eat exactly the same calories as they were exercising out every day would get inexorably thinner or fatter all the time. And we also know this doesn’t happen.

Calorie in out is 100% true no exceptions

I can introduce you to several exceptions if you like?

Calories in calories out is a pretty good place to start. Yes biochemistry (glycolysis, gluconeogenesis) plays a part but if you force your body into deficit it has to trigger the biochemical processes needed to convert fat reserves into energy to fuel the body which includes transcription on demand of the genes needed to produce the proteins needed to do this. The more your body is used to doing this the more quickly it can do it on demand, so those that chug the ale after a ride will find it harder to burn fat when they do d code to abstain. But then I’m just a biochemist so what do I know!?

Ride more, eat less, get used to being in deficit (hunger) and you’ll lose weight. It’s that simple.

v8ninety
I’m not entirely convinced by the simple (simplistic?) calories in/calories out equation…

Not many fat people came out of Auschwitz, so while there are other factors involved it looks like if you restrict calories sufficiently, weight loss occurs and those other factors are secondary.

Not much MTBing went on in Auschwitz either, pretty stupid example for people who aren’t in concentration camps and don’t wish to live like that.

Sometimes, eating less reduces your ability to move at your normal rate, and can also reduce your BME to compensate for less intake. And this is governed by all sorts of processes that you can’t control easily.

Of course ‘eat less move more’ is a good starting point. It’s not wrong, but it’s far from the whole story.

Someone told me once that your body has so many fat cells, cells which are capable of storing fat. Once these get full your body makes more fat cells so you can store more fat. Once these get full your body creates more etc etc.

But when you get rid of fat your body doesn’t reduce the number of fat cells you have it keeps them there forever, sitting empty just in case it needs them again.

When you lose weight and get rid of the fat, those empty cells cause you to want to fill them again (chemical signal, hormones, whatever sciencey reason) hence why 90%+ of people who lose lots of fat eventually go on to put it all back again plus a bit more on top.

Don’t know if that’s true or not, but it was an interesing pub conversation.

It’s really not – because if that were true then everyone who over-ate would get fat, and we know that doesn’t happen.

Then they’re not over-eating, surely?

calories in has to equal calories out but it’s complicated by the fact that your body doesn’t absorb all of the calories that you eat and calories out is a mix of energy burned in exercise, bmr and stuff excreted.  As far as I can see what some of these funny diets can do is mess with those ratios so both methods work.  Eating less is the most basic method of reducing calories in but so are various diets that can mess with how your body processes food.

Best method I’ve found is reducing your intake slightly.  You end up being slightly hungry most of the time but that becomes normal and doesn’t bother you any more.  weight comes down

Beer however is another issue 🙁

Not many fat people came out of Auschwitz, so while there are other factors involved it looks like if you restrict calories sufficiently, weight loss occurs and those other factors are secondary.

This.

In spite of being very active I was Obese all my life until last winter. Then I got a grip and started to think about what I eat and drink. In 6 months I lost 3 stone and 10 months on I’m not even overweight.

There is no doubt in my mind that thinking about weightloss as energy in/energy out is the only sane way to think about it. I’m sure there are other minor factors but as far as I know they can’t be controlled so what’s the point thinking about them?

Also those other factors can only apply at the top end: ie – Some people are able to eat more without putting on weight. At the bottom end it makes no odds, if you’re in deficit you *will* lose weight no matter how slow your metabolism is.

..and another thing. How the hell did a Country where obesity is one of the biggest health problems get so worried about Anorexia which is comparatively rare…