Calories aren't an appropriate measure of human nutrition. At best, it's a proxy for mass, but is otherwise useless if you understand anything about how obesit

Calories aren't an appropriate measure of human nutrition. At best, it's a proxy for mass, but is otherwise useless if you understand anything about how obesity actually works. You don't seem to understand it if you think that a unit of heat can measure how fat someone will get. The human body reacts with hormones depending on what you eat. It is not at all aware of how much energy you're consuming. All it is doing is delegating mass towards processes that need that mass. Depending on what you eat, that mass will be used differently. For instance, if you eat protein, that protein will not only be used for a wide variety of things in your body, but it can be used to supply the blood with glucose through a process called glucconeogenesis. However, this is a lossy process, since it takes 3 ATPs to ultimately get 2 ATPs out of a conversion of protein to gluccose. Since the body needs protein to build cells, it will primarily use glucconeogenesis to meet demand of glucose. On the other hand, if you consume carbohydrates or sugar, you are supplying the body with glucose that it didn't demand, and it's going to respond with insulin to handle that supply, causing cells to uptake that glucose (including fat cells). If, however, you decide to eat nothing but fat, it will ironically be difficult to actually get fatter that way because the body responds only weakly to the presence of fat with insulin. Yet fat has more energy per gram than either sugar or protein. Fiber also contains "calories", yet interferes with the absorption of other substrates and a minuscule amount is fermented and transformed into fatty acid. Consuming different substrates together also affects how food mass is handled. Notoriously, fat and carbs, when consumed together, are cross-inhibiting, meaning it takes and even greater amount of insulin for cells to uptake them. This is the primary dysfunction behind type-2 diabetes. And if you want to waste away, eat as many "calories" as you want of leaves. There's still "calories" in kale and spinach, but that doesn't mean it will translate to obesity or a body composition any sane person would want. If you don't think the leaves and stalks of plants have plenty of "calories", try drying some out and lighting them on fire. In other words, it comes down to what you eat, not so much the quantity. A fatty steak and a jelly doughnut create very different metabolic conditions that are not equivalent in terms of being obesogenic. An individual who eats nothing but jelly doughnuts for a month will see a different outcome from the individual who eats fatty steaks in the same time period, even if the latter individual eats more "calories" worth of mass.