Used via Creative Commons license
Source: Used via Creative Commons license

Over the last few weeks, I've written about 3 of the 4 most popular lies around weight and health. It's time to look at the biggest of them all.

Lie #4: Diets make you thinner and healthier.

Truth #4: No and no. By now you likely have heard the statistic: Only 3 to 5 percent of people who diet keep the weight off for more than 3 years. That means your chance of surviving metastatic lung cancer is higher than your chance of maintaining a major weight loss. By "major" I mean 30 pounds or more, which is the criterion used by the National Weight Control Registry to track "maintainers." The NWCR requires only that people keep it off for a year to qualify for the registry, and what's not obvious from reading the registry is that many people on the list are continually regaining and losing.

So unless you're one of the 5 percenters, dieting will not make you thinnner. On the contrary—it makes most people fatter over time, especially kids and teens. The younger kids are when they start to diet, the heavier they tend to become, and the higher their chance of developing risky behaviors like purging, taking laxatives, smoking, disordered eating, and overexercising.1, 2  And dieting kids and teens are also less likely to pursue healthy behaviors, like regular exercise and eating balanced meals.3

So dieting not only doesn't make you thinner, it usually makes you fatter. But at least you're healthier, right?

Wrong again. Researchers at UCLA studied people who'd lost weight intentionally, looking at common health "biomarkers" like blood pressure, glucose levels, cholesterol, and triglycerides. They expected the dieters to have better numbers even if they hadn't kept off the weight. They found, instead, no relationship between weight loss (or gain) and health outcomes.4 "We had some trouble getting the study published,” deadpans A. Janet Tomiyama, the study's lead author.

Tomiyama’s study doesn’t mean that weight loss never benefits health, of course. Some people who intentionally lose weight see improvements in blood pressure or glucose levels or cholesterol or joint pain. It does underline the fact that health is individual. What’s healthy for me might not be healthy for you, and vice versa. So our knee-jerk response to every health problem—lose weight!—might just need to be reconsidered.

Read more in my new book, Body of Truth: How Science, History, and Culture Drive Our Obsession with Weight—and What We Can Do About It.

1. Dianne Neumark-Sztainer et al., “Dieting and Disordered Eating Behaviors from Adolescence to Young Adulthood: Findings from a 10-Year Longitudinal Study,” Journal of the American Dietetic Association 111 (2011): 1004–1011.

2. E. Enriquez, G. E. Duncan, and E. A. Schur, “Age at Dieting Onset, Body Mass Index, and Dieting Practices. A Twin Study,” Appetite 71 (2013): 301–306.

3. Dianne Neumark-Sztainer, “Dieting and Unhealthy Weight Control Behaviors During Adolescence,” Journal of Adolescent Health (2012): 80–86.

4. Tomiyama, A. Janet, Britt Ahlstrom, and Traci Mann. “Long-Term Effects of Dieting: Is Weight Loss Related to Health?” Social and Personality Psychology Compass  7 (2013): 861–877.

About the Author

Harriet Brown

Harriet Brown is the author of Body of Truth: How Science, History, and Culture Drive Our Obsession with Weight—and What We Can Do About It, Brave Girl Eating, and other books. 

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