Without additional assumptions, the calories-in/calories-out identity is not by itself a theory, but this useful identify can tempt people into bad theories. In “Nina Teicholz on the Bankruptcy of Counting Calories” I write:
The calories-in/calories out identity is typically thought of this way:
Weight Gain in Calories = Calories Consumed - Calories Expended
What sneaks in with this arrangement of the identity is the questionable idea that calories consumed and calories expended are fixed quantities not subject to any deeper forces. Rearranging the identity gives a different perspective:
Calories Expended = Calories Consumed + Weight Loss in Calories
This rearrangement subtly hints at the idea that, holding calories consumed fixed, effective weight-loss that puts a lot of fatty acids and ketones into the blood stream from metabolized body fat might make one feel more energetic and so raise calories expended. Conversely, relatively ineffective weight loss combined with a low level of calories consumed will lead to internal starvation with all kinds of body signals going out to discourage energy expenditure and encourage the consumption of more calories. Those body signals are exactly the kinds of signals that can cause suffering.
In the equations above, an important aspect of “calories expended” is that the more calories expended, the more tolerable it is likely to be for the individual. In order to get a low level of calories expended, body signals have to lower the metabolism, which makes an individual feel tired and listless so they will keep effort levels low. Low levels of “calories expended” are usually an unpleasant experience.
The Framingham State Food Study provides some of the best evidence that two different diets, both adjusted to keep weight steady, can lead to different amounts of calories expended. This is an impressive study: it “tightly controlled what people ate for 30 weeks, providing them with fully prepared food-service meals.” Here is the key result:
Over the 20 weeks, total energy expenditure (measured with the doubly labeled water method) was significantly greater on the low-carb versus the high-carb diet. At the same average body weight, participants who consumed the low-carb diet burned about 250 kilocalories a day more than those on the high-carb diet.
That is more than a 10% increase in calories expended for a typical person. (Women on average consume and expend about 2000 calories per day; men consume and expend about 2500 calories per day.) Here is how David Ludwig interprets the result:
“This is the largest and longest feeding study to test the ‘Carbohydrate-Insulin Model,’ which provides a new way to think about and treat obesity … According to this model, the processed carbohydrates that flooded our diets during the low-fat era have raised insulin levels, driving fat cells to store excessive calories. With fewer calories available to the rest of the body, hunger increases and metabolism slows — a recipe for weight gain.”
I am excited about the other new clinical trial an overlapping team is involved in: it randomizes experimental subjects to a very-low-carb, a high carb/low sugar or a high carb/high sugar diet.
Don’t miss my other posts on diet and health:
I. The Basics
II. Sugar as a Slow Poison
III. Anti-Cancer Eating
IV. Eating Tips
V. Calories In/Calories Out
VIII. Debates about Particular Foods and about Exercise
Julia Belluz and Javier Zarracina: Why You'll Be Disappointed If You Are Exercising to Lose Weight, Explained with 60+ Studies (my retitling of the article this links to)
IX. Gary Taubes
X. Twitter Discussions
XI. On My Interest in Diet and Health
See the last section of "Five Books That Have Changed My Life" and the podcast "Miles Kimball Explains to Tracy Alloway and Joe Weisenthal Why Losing Weight Is Like Defeating Inflation." If you want to know how I got interested in diet and health and fighting obesity and a little more about my own experience with weight gain and weight loss, see “Diana Kimball: Listening Creates Possibilities” and my post "A Barycentric Autobiography.