calories in - calories out was debunked a while ago. Different types of food and diet cause different degrees of weight gain or loss.

For an extreme example compare 100 calories of glucose to 100 calories of fibre, both are types of sugar. The fibre contains an extra electron that acts like a shell, and the body has to expend energy breaking that bond to make it digestible. So most fibre passes through you without affecting your weight.

The most useful measure of food is the Glycemic Load. Not Glycemic Index which is a measure of the net glucose in the food. Glycemic Load is a measure of how the body responds to the food. E.g. cold potatoes have the same calories and GI as hot potatoes, but their measured GL is actually lower, so cold potatoes are better for controlling weight.

> calories in - calories out was debunked a while ago.

Not really, it's just that calories-in is worst-case that's what's on the foods box, you cannot magically produce more energy but it's well known that not everything can be processed by the metabolism with the same efficiency.

So with extremes like your example the difference is naturally huge, but that doesn't matter in practice if one balances their consumption just somewhat it averages out and approaches something between upper (100%) and lower (0%) of efficiency, and in reality it rather close to the upper bound (averaged) as our metabolisms are quite efficient with the food most humans actually put into them.

Your glycemic index rule holds does not violate the calories in calories out rule, it's just more precise regarding the actual upper bound.

Not really. E.g. look at my second example, cold potatoes vs hot potatoes. Same calories, same exact ingredients, but hot potatoes are significantly worse than cold potatoes.

I dont have the link to hand, but there is a GL database maintained by Harvard, I think, that demonstrates this. I will look it up later for you.

It’s still calories in vs calories out. What changed is that our understanding of what determines calories in and calories out has become more nuanced. For instance, your examples

My examples demonstrate that calories in / calories out is false. I don't quite get your point? A calorie is a measure of the useful energy released from burning stuff in a furnace. It was invented to compare the efficiency of different fuels for steam engines. It has no relevance to humans, who don't use a furnace and steam power, but a complex chain of cascading chemical reactions.

What I mean is that "calories in" is not literally calculated by the total energy you put in your mouth, but rather the energy your body absorbs from that. And as you note that might be different based on the food, how the food is prepared, content of the food, etc.

Likewise "calories out" is not literally calculated by adding up your movement & exercise. We know that things like hormonal levels, etc can all impact how much energy your body is expending.

> calories in - calories out was debunked a while ago.

No, it wasn't. It's the generally accepted model of human weight gain. It's what most scientists who study this topic believe to be true. (And really, it's the only model that makes any sense, and is incredibly easy to test)

They only people who disagree with this model are considered to be outside the mainstream of science. They might be right (I don't think so though) - but it's certainly not debunked.

Obviously if you eat fewer calories than you burn, you’ll lose weight. But the inverse is not necessarily true. It’s possible to consume more calories than you burn and still lose weight, because your body doesn’t necessarily utilize all calories consumed.

Just because the USDA is 30 years behind the science doesn't make them right. There are hundreds of studies now debunking it. Do you really want to contend that 100 calories of fibre is the same as 100 calories of glucose? Ridiculous. In fact, the calories model never had broad academic support. Ansel Keys research is a joke today.

>The fibre contains an extra electron that acts like a shell, and the body has to expend energy breaking that bond to make it digestible.

I'm not a nutritional expert, but...this sounds like bro science. Do you have a source for this, or can someone who knows this better speak to it?

Not sure about exact process. But whole fruit has dramatically lower glycemic index than juice of the same fruit.

Guess what else has massive effect on metabolism? Exercise.

Also, various workouts have a lot of other important effects. Increasing bone strength, improving body resistance to inflammatory processes, developing micro vascular system… simply managing calorie in/out ratio won’t get you any of this. And dropping weight in a dumb way may do more harm than good.