Rethinking “Calories In, Calories Out”

I came across an interesting new paper on SSRN looking at caloric intake and obesity across populations “Macronutrients and Obesity: Revisiting the Calories in, Calories out Framework” by Daniel Riera-Crichton and Nathan Tefft. Here’s the abstract:

Recent clinical research has studied weight responses to varying diet composition, but the contribution of changes in macronutrient intake and physical activity to rising population weight remains unknown. Research on the economics of obesity typically assumes a “calories in, calories out” framework, but a richer weight production model separating caloric intake into carbohydrates, fat, and protein, has not been explored. To estimate the contributions of changes in macronutrient intake and physical activity to changes in population weight, we conducted dynamic time series and structural VAR analyses of U.S. data between 1974 and 2006 and a panel analysis of 164 countries between 2001 and 2010. Findings from all analyses suggest that increases in carbohydrates are most strongly and positively associated with increases in obesity prevalence even when controlling for changes in total caloric intake and occupation-related physical activity. If anything, increases in fat intake are associated with decreases in population weight.

The fat finding may be counter-intuitive, but the finding that increases in carbohydrate consumption correlate more strongly with increases in obesity is not surprising at all. It conforms with much that’s been learned about weight gain and weight loss in recent years.