Does Eating Fat Make You Fat?

Dr. Sears' Blog: Does Eating Fat Make You Fat?

The 1990s brought with it an era of people fearing fat. After all, “if no fat touches my lips, then no fat reaches my hips.” Harvard took charge of this debate and declared war against fat, especially saturated fat. Manufacturers created everything from fat-free yogurt to cookies. Overall, fat intake did decrease nationwide during this time, but the waist lines of the U.S. population continued to expand. Despite recent reports about the Mediterranean diet and the benefits of monounsaturated fats, the low-fat craze still has many hardwired to think that eating higher-fat foods will make them fat. Although calorically speaking, fat is more energy dense than carbohydrates and protein, a recent study may help to ease people’s preconceived notions on the role of fat and weight gain.

There have been inconsistent findings in the literature on whether the type of fat consumed influences weight change. Even studies in which poly and monounsaturated fats have been substituted for saturated fat to lower cardiovascular disease were equally wishy-washy (1). In fact, a recent study published in the American Journal of Clinical Nutrition questions whether dietary fat played a role in future weight gain (2). Of the more than 89,000 men and women studied, overall fat consumption ranged from 31.5 percent to 36.5 percent. No matter the total fat intake or the type of fat consumed, there was no effect on weight gain over the long term in either men or women. Maybe fat doesn’t make you fat.

This only proves you can always tell a Harvard man, you just can’t tell him very much.


  1. Siri-Tarino PW, Sun Q, Hu FB, Krauss RM. Saturated fat, carbohydrate, and cardiovascular disease. Am J Clin Nutr. 2010 Jan 20.
  2. Forouhi NG, Sharp SJ, Du H, van der A DL, Halkjaer J, Schulze MB, Tjønneland A, Overvad K, Jakobsen MU, Boeing H, Buijsse B, Palli D, Masala G, Feskens EJ, Sørensen TI, Wareham NJ. Dietary fat intake and subsequent weight change in adults: results from the European Prospective Investigation into Cancer and Nutrition cohorts. Am J Clin Nutr. 2009 Dec;90(6):1632-41.

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About Dr. Barry Sears

Dr. Barry Sears is a leading authority on the impact of the diet on hormonal response, genetic expression, and inflammation. A former research scientist at the Boston University School of Medicine and the Massachusetts Institute of Technology, Dr. Sears has dedicated his research efforts over the past 45 years to the study of lipids. He has published 40 scientific articles and holds 14 U.S. patents in the areas of intravenous drug delivery systems and hormonal regulation for the treatment of cardiovascular disease. He has also written 14 books, including the New York Times #1 best-seller, The Zone, which have sold more than 6 million copies in the U.S. and have been translated into 22 different languages.

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