History doesn’t support the idea that we’re simply eating more calories today. Going as far back as the American civil war we have records of what people were eating and what their general BMI was, and there is no causal link demonstrating that we are eating more today than we were then.

To the contrary, there is evidence that we were eating more calories in the past than we are today, and that general levels of exercise are actually greater today than they were in the past as an average across the populace.

Honestly, read the articles. There is a ton of information in there challenging what we “know” that no summary will do justice.

Here’s an excerpt:

> A popular theory of obesity is that it’s simply a question of calories in versus calories out (CICO). You eat a certain number of calories every day, and you expend some number of calories based on your metabolic needs and physical activity. If you eat more calories than you expend, you store the excess as fat and gain weight, and if you expend more than you eat, you burn fat and lose weight.

> This perspective assumes that the body stores every extra calorie you eat as body fat, and that it doesn’t have any tools for using more or less energy as the need arises. But this isn’t the case. Your body has the ability to regulate things like its temperature, and it has similar tools to regulate body fatness. When we look closely, it turns out that “calories in, calories out” doesn’t match the actual facts of consumption and weight gain.

> “This model seems to exist mostly to make lean people feel smug,” writes Stephen Guyenet, “since it attributes their leanness entirely to wise voluntary decisions and a strong character. I think at this point, few people in the research world believe the CICO model.”