Just a fad? Do popular diets actually work?

The Bottom Line

  • There are countless popular diets out there, but for many of these diets there is a lack of research available to determine if they really help people lose weight, and if they are safe to practice. 
  • The Atkins Diet may be effective in producing weight loss in the short-term and long-term, but questions around safety remain.

Do you need to lose weight? If so, you’re not alone. The number of people carrying excess pounds is on the rise around the globe (1). In Canada, roughly 34% of Canadians are overweight, and an additional 20% are obese (2). This amounts to a weighty problem—extra pounds carry with them an increased risk of many health problems, including heart disease, diabetes, and high blood pressure.

In a bid to lose weight, many people turn to trendy diets. There is no shortage of options out there—a whopping 38 popular diets were listed in a recent U.S. News & World Report of “Best Weight-Loss Diets”. Although popular, experts have questioned if these diets really work and if they are safe (3).

A recent systematic review took a closer look at which of the popular diets outlined in the U.S. News & World Report are backed by evidence when they are practiced in their original format – meaning without calorie targets, meal replacements, commercial products, or structured exercise programs beyond what the diet itself recommends (3). It turns out that of the 20 diets that met the inclusion criteria, only seven—Atkins, DASH, Glycemic-index, Mediterranean, Ornish, Paleolithic, and Zone— had undergone rigorous testing.

The Mediterranean Diet includes mostly fruits and vegetables, whole grains, beans, nuts, and olive oil (3). The Paleolithic Diet emphasizes protein and discourages carbs (4). The Dietary Approaches to Stop Hypertension (DASH) Diet includes foods that are high in fiber and low in fats, such as fruits, vegetables, and low-fat dairy products (5). The Glycemic-Index Diet includes low glycemic foods like non-starchy vegetables and beans (6). The Ornish Diet limits the amount of fat that you can eat (2). Lastly, the Zone Diet recommends eating a lower amount of carbs (7).

So, what’s the bottom line? Can these diets help you lose weight and keep it off?

What the research tells us

The review evaluated which popular diets produce weight loss in the short (within 6 months) and long-term (beyond a year) (3). It covered seven different types of diets: Atkins, DASH, Glycemic-index, Mediterranean, Ornish, Paleolithic, and Zone. Although there are plenty of other popular diets out there, many have not been well-studied or studied at all. All the studies included in this review required people to stick with their diets for at least 12 weeks (3).

Of all these diets, Atkins—which focusses on limiting carbs (7)—was supported by the most evidence that it can lead to short-term and long-term weight loss (3).

As for the other 6 diets, there is simply not enough evidence to say if they are effective or not. Two diets—the Mediterranean and Paleolithic diets—were promising, as both were associated with short-and long-term weight loss, but based on only one study for each outcome. For the Zone Diet, evidence was mixed, but any weight loss may be limited to the short-term. In contrast, the DASH, Glycemic-index, and Ornish diets did not produce any meaningful effect over time. Although this review found that a low-carb diet was successful for weight loss, the safety of this type of diet, as well as other popular diets still needs to be assessed. People considering trendy diets should also take stock of the fact that participants in many of the studies had a hard time actually sticking to the diets, with only a small number maintaining the diet beyond the study (3).

The verdict: while there are many diets out there that promise to trim your waistline, only Atkins is supported by evidence that it can produce both short-and long-term weight loss. However, the safety of Atkins and other popular diets is unknown at this time.

Featured Resources


Get the latest content first. Sign up for free weekly email alerts.
Author Details


  1. Mann T, Tomiyama AJ, Westling E, et al. Medicare’s search for effective obesity treatments: Diets are not the answer. Am Psychol. 2007; 62(3):220-233.
  2. Statistics Canada. Health indicators, annual estimates, 2003 – 2014. [Internet] 2018. [cited November 2018]. Available from https://www150.statcan.gc.ca/t1/tbl1/en/tv.action?pid=1310045101
  3. Anton SD, Hida A, Heekin K, et al. Effects of popular diets without specific calorie targets on weight loss outcomes: Systematic review if findings from clinical trials. Nutrients. 2017; 9(8): 822. doi: 10.3390/nu9080822. 
  4. Mellberg C, Sandberg S, Ryberg M, et al. Long-term effects of a Paleolithis-type diet in obese postmenopausal women: A two-year randomized trial. Eur J Clin Nutr. 2014; 68(3):350-357. doi: 10.1038/ejcn.2013.290.
  5. Blumenthal JA, Babyak MA, Sherwood A, et al. The effects of the DASH diet alone and in combination with exercise and caloric restriction on insulin sensitivity and lipids. Hypertension. 2010; 55(5):1199-1205. doi: 10.1161/hypertensionaha.109.149153. 
  6. Ebbeling CB, Leidig MM, Feldman HA, et al. Effects of a low-glycemic load vs low-fat iet in obese young adults: A randomized trial. JAJA. 2007; 297(19):2092-2102. 
  7. Dansinger ML, Gleason JA, Griffith JL, et al. Comparison of the Atkins, Ornish, Weight Watchers, and Zone diets for weight loss and heart disease risk reduction: A randomized trial. JAMA. 2005; 293(1):43-53. 

DISCLAIMER: These summaries are provided for informational purposes only. They are not a substitute for advice from your own health care professional. The summaries may be reproduced for not-for-profit educational purposes only. Any other uses must be approved by the McMaster Optimal Aging Portal (info@mcmasteroptimalaging.org).

Many of our Blog Posts were written before the COVID-19 pandemic and thus do not necessarily reflect the latest public health recommendations. While the content of new and old blogs identify activities that support optimal aging, it is important to defer to the most current public health recommendations. Some of the activities suggested within these blogs may need to be modified or avoided altogether to comply with changing public health recommendations. To view the latest updates from the Public Health Agency of Canada, please visit their website.