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The Truth Behind Fad Diets

Is dieting making you fat?

Losing weight with commercial diets has been consistently popular amongst many people wanting to shed pounds. Among these are low-calorie diets, juice fasts, soup-only diets, etc. Many of us are also familiar with advertisements for such diets promising to lose “x” amount of lbs. in “x” amount of days. However, aside from their “money-back guaranteed” offer if weight loss isn’t achieved, these fad diets all have something else in common: they are deprivation diets. They all focus on taking something away. Whether it’s “No fats for a month” or “1,000 calories a day”, these diets are designed such that a person can sustain this type of eating for a short time, but afterwards their bodies will need much more food to compensate for the loss.

Let’s say that you’re someone who desperately wants to lose those extra 15 lbs. in order to reach your “ideal” weight. A commercial diet that guarantees that you’ll lose those 15 lbs in a month may sound enticing because, after all, at the end of the month you’ll be 15 lbs lighter. But would you still take this diet up on their offer if you knew that 2 years from now you’ll have regained those 15 lbs plus an additional 10 lbs.? What started off with you being 15 lbs over your ideal weight could end in you being 25 lbs. over your ideal weight.

This is the truth behind fad diets: in general, you will lose weight in a short period of time, but chances are that you will gain back more weight than you had originally lost. One study found that, overall, short-term diets could help you lose 5%-10% of your weight. This means that if you weigh 140 lbs., you’d be able to lose 7-14 lbs. in a relatively short amount of time. The problem then becomes that once people lose their desired amount of weight or once the “money-back guaranteed” month is over, they will usually stop the diet and go back to eating how they normally ate before the diet. A study in which researchers significantly decreased the subjects’ caloric intake (much like many commercial diets today) found that after 5 years, 83% showed more weight gained than originally lost! That means that the majority of the people in the study gained back more weight than they lost.

So what if before you gain the extra weight you start another commercial diet? Unfortunately, researchers in 2012 found even more evidence showing that more short-term dieting results in increases in amount of weight that will be gained. Shockingly, the amount of weight can be potentially gained after this type of dieting behavior is independent of genetic factors. This means that even if you and your entire family have always been normal-weight, these fad-dieting behaviors can lead you to become overweight.

Weight cycling is another outcome of going through many short-term diets and has many negative consequences on its own. For example, for those who are predisposed to being overweight, weight cycling will exacerbate one’s predisposition to obesity. Moreover, while dieting for a long period of time (instead of just for short terms) will prevent weight cycling, long-term dieters do not fare much better than nondieters by only keeping off an average of 3.7 lbs. after 3 years.

These findings may paint a gloomy picture for people struggling to lose weight, but weight loss still is possible through other means. It is important to note that these fad diets all are aimed for intentional weight losses (i.e. dieting for the sole purpose of losing weight). It is the intentional weight loss aspect of these diets that are causing the weight regain along with other physiological detriments, such as sudden increases in the stress hormone cortisol. The key is to not deprive ourselves of foods that our bodies need, but to focus more on increasing on the good things that we put into our bodies. This includes adding more healthy varieties of food that our bodies actually need (i.e. cut out the unnecessary artificial preservatives, salts, and sugars from our diets instead of cutting calories) and adding more daily physical exercise that our bodies also need. From a series of studies on weight-loss approaches, the only intervention that showed promising results was the one that emphasized for a healthier lifestyle through healthy foods and regular exercise. Not only does this target excessive weight issues, but this healthier lifestyle also reduces the incidences of diabetes, heart conditions, and stress.


Tomiyama, A. J., Mann, T., Vinas, D., Hunger, J. M., DeJager, J., & Taylor, S. E. (2010). Low calorie dieting increases cortisol. Psychosomatic medicine, 72(4), 357-364.

Mann, T., Tomiyama, A. J., Westling, E., Lew, A. M., Samuels, B., & Chatman, J. (2007). Medicare’s search for effective obesity treatments. Am Psychol, 62(3), 220-233.

Pietiläinen, K. H., Saarni, S. E., Kaprio, J., & Rissanen, A. (2011). Does dieting make you fat? A twin study. International Journal of Obesity, 36(3), 456-464.

Dr. Nicole Avena is a research neuroscientist/psychologist and expert in the fields of nutrition, diet and addiction. She has published over 60 scholarly journal articles, as well as several book chapters on topics related to food, addiction, obesity and eating disorders. She recently edited the book, Animal Models of Eating Disorders (Springer/Humana Press, 2013), and she has a book Why Diets Fail (Ten Speed/Crown) available for preorder now and to be released in January, 2014. Her research achievements have been honored by awards from several groups including the New York Academy of Sciences, the American Psychological Association, the National Institute on Drug Abuse, and her research has been funded by the National Institutes of Health (NIH) and National Eating Disorders Association.




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