How do people lose weight?

Most diets fail. I’m not sure if this “fact” is actually true, but it’s repeated often enough to make me think there’s something to it. It also just seems likely to be true. During my second year of university, I gained about 20 - 30 lbs and tried to shed it quickly by adopting a Very Low Calorie Diet, something recommended for morbidly obese people. I wasn’t morbidly obese, I was just on the cusp of being overweight - my BMI was probably around 24 or 24.5 (overweight is 25). But my optimiser brain made me think that it was a waste of time spending half a year trying to lose the weight I’d gained when I could do it in a couple of months.

It’s an odd feeling, not eating very much. I only tried it for a few weeks, but it really had a remarkable impact on the way that I behaved: instead of playing video games or watching YouTube videos as a way to relax in the evening, I looked up recipes and watched television shows about extreme diets. You don’t really feel hungry in the way that you do when you’ve missed a meal, it’s more like parts of your brain become entirely dedicated to thinking about anything to do with food.

I would browse food-porn subreddits, read the Michelin guide to figure out where I would go when the diet was over, and so on. The diet ended when I couldn’t bear it any longer and ended up binging a load of junk food. But it was weird, it wasn’t what I expected at all when I started trying to lose weight - you become a new person with a weird and obsessive interest in food that you never had before, and you aren’t allowed to get your old interests and hobbies back until you eat enough to feel satiated.

This isn’t just some weird experience that was unique to me. Children and teenagers who are deficient in the hormone Leptin, which is responsible for the feeling of fullness after a meal, have a more extreme version of the same experience (h/t SSC):

Usually they are of normal birth weight and then they’re very, very hungry from the first weeks and months of life. By age one, they have obesity. By age two, they weigh 55-65 pounds, and their obesity only accelerates from there. While a normal child may be about 25% fat, and a typical child with obesity may be 40% fat, leptin-deficient children are up to 60% fat. Farooqi explains that the primary reason leptin-deficient children develop obesity is that they have “an incredible drive to eat”…leptin-deficient children are nearly always hungry, and they almost always want to eat, even shortly after meals. Their appetite is so exaggerated that it’s almost impossible to put them on a diet: if their food is restricted, they find some way to eat, including retrieving stale morsels from the trash can and gnawing on fish sticks directly from the freezer. This is the desperation of starvation […]

Unlike normal teenagers, those with leptin deficiency don’t have much interest in films, dating, or other teenage pursuits. They want to talk about food, about recipes. “Everything they do, think about, talk about, has to do with food” says [Dr.] Farooqi. This shows that the [leptin system] does much more than simply regulate appetite – it’s so deeply rooted in the brain that it has the ability to hijack a broad swath of brain functions, including emotions and cognition.

The same thing happens to people who don’t eat much - here’s a summary of the psychological consequences of the Minnesota Starvation Experiment:

Over the course of their weight loss, Keys’s subjects developed a remarkable obsession with food. In addition to their inescapable, gnawing hunger, their conversations, thoughts, fantasies, and dreams revolved around food and eating – part of a phenomenon Keys called “semi-starvation neurosis”. They became fascinated by recipes and cookbooks, and some even began collecting cooking utensils. Like leptin-deficient adolescents, their lives revolved around food. Also like leptin-deficient adolescents, they had very low leptin levels due to their semi-starved state.

So, I can believe that diets don't work. Or at least, it seems unlikely that most extreme diets are effective - it is completely unbearable to be thinking about food all the time, and I imagine very few people have the will-power to remain on a Very Low Calorie Diet. (Note: even if you do think you have the willpower, it’s unhealthy to actually do this, so please don’t).

So, how do people actually lose weight? The obvious answer is that people adopt sustainable diets where they eat a bit less and exercise a bit more, and move from being in a slight calorie surplus to being in a slight calorie deficit without putting too much of a toll on their body. And yeah… maybe? But as far as I can tell, not many people I know have lost weight like that, with small changes at the margins. Instead, I think the most common way that people I know have lost weight is by making a major lifestyle change that naturally leads to weight-loss as a side-effect.

Examples include: giving up alcohol, getting into long-distance running as a hobby, and going vegan. In The Hungry Brain, the book that is being quoted above (which I haven’t actually read in full, I’ve just read Scott’s review that’s linked above), apparently one of the main (half-joking) recommendations is just to eat extremely bland food. The reasoning given is that most food you eat is optimised to make you want to eat more of it: salty fries are paired with umami-rich cheeseburgers with a fatty and sugary milkshake as the drink, so of course you’re going to gorge yourself. How about you just stick to Huel and enjoy the resulting weight loss?

Obviously, nobody is going to do this for very long. Eating very small amounts of food is hellish, but is a pure Huel diet much better? It probably won’t lead to a weird obsession with cookery shows, but even so, it sounds horrendous. So my proposal for losing weight, based mostly on hunches rather than research, is that you ought to make some huge lifestyle change that isn’t actually that bad and will naturally lead to weight loss without much extra effort. I mean, you shouldn’t actually do these, but I do wonder if they would work. Here are some random suggestions:

• There seems to be pretty good evidence that living at a high altitude (3500m - 5300m) is linked to weight-loss without exercise. Here’s a meta-analysis that finds that weight loss across 41 studies for people living at high altitudes is between 7.7kg and 0.01kg for durations between 4 and 75 days. And here’s the correlation between altitude and obesity in the United States:

• I’ve talked about the benefits of getting on ADHD medication before (even if you don’t have ADHD). Another benefit I’ve never mentioned is that most stimulants do seem to be linked to weight loss. While I’m not recommending that you use amphetamines for weight loss, I do think it’s pretty likely that getting on ADHD medication is a good idea for many people, and I think there’s decent evidence it’s causally linked to (at least short-term) weight loss.

• As mentioned, I’ve noticed that people who go vegan, start an exercise hobby not for the purpose of losing weight (especially long-distance running), and give up alcohol all tend to shed fat fairly quickly. The reasons here seem fairly straight forward, although I’m most sceptical of long-distance running - seems like the extra calorie expenditure might result in eating even more than you burnt off.

I would be interested to see the results of a study comparing weight loss among a group who made a lifestyle change like the ones above to a group who tried to lose weight using the standard ‘sustainable and incremental changes’ advice. I think I’d bet on more weight loss in the first group. (Again: I don’t actually recommend doing this stuff, I’m just interested to know how it would compare to ordinary dieting).