Fast Take: Weight Loss “Without Giving Up a Single Calorie?”

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“How Americans can lose a lot of weight without giving up a single calorie” is a headline that should be setting off significant mental warning alarms. In fact, in War on Science Part 1, nutrition experts flagged this exact kind of language as indicative of a questionable ‘weight loss quick fix.’ The headline appeared yesterday in the Washington Post, citing a study by an agricultural economist on the relationship between BMI and different cultural diets…without considering physical activity or energy expenditure. Here, we offer a fast-take on the article. Consider yourself prepped for when your friend tries to use this to justify a weight loss plan that doesn’t account for calories!


1. There are TWO pieces to the calorie equation, not just one.

The biggest red flag to us is Rehkamp’s disclaimer that the mathematical model also “may be capturing other lifestyle factors associated with each diet, such as physical activity or eating habits in the country.” Those eating plant-based diets are perfectly likely to have drastically different lifestyles including more physical activity than the average American, and the amount of calories you’re expending is well-documented to have a major impact on weight management. The USDA has a great guide on balancing calories to manage weight. Additionally, we actually just released a guide on this energy balance.


2. You’ve got to start with real-world assumptions.

Furthermore, this model assumes a daily diet of nearly 3,700 calories, far above the average calorie consumption of Americans indicating that the methods used to create these claims are based on scenarios that are not applicable to the daily calorie consumption.


3. The body of science is clear on calories.

Finally, it is well supported that a calorie is a calorie regardless of source, so these findings are not supported by the totality of research. Together, this new study shows the importance of critically reviewing how the results were generated and how the findings stand up to the totality of science.


Weight loss can be intimidating, which makes it tempting to look for those ‘quick fixes.’ But to dive in without understanding the science on energy balance sets you up for more frustration down the line. Suspect headlines like this one do that too.

Questions on energy balance and calories? Dig into our resources here.

This article was written by Liz Caselli-Mechael, MS and reviewed by Tamika Sims, PhD. It includes contributions from Megan Meyer, PhD.