The authors of The Flat Belly Diet claim that by eating monounsaturated fat (MUFAs) at every meal and eating a reduced calorie diet, participants can lose weight and in particular, belly fat, at a high rate and without exercise. Liz Vaccariello, the editor of Prevention magazine, and Cynthia Sass, a nutritionist and MPH authored the book and ascribe many beneficial properties to MUFAs. While the diet is low is calories and likely to help people who follow it lose weight, the claims in the book are misleading and some of the advice is downright dangerous.
The diet begins with a four-day “anti-bloat” jumpstart, during which dieters eat prescribed meals consisting of 1200 calories per day and avoid foods and beverages that cause water retention and bloating. Dieters must also drink “sassy water” which contains ginger, lemon, cucumbers, and spearmint leaves. (While sassy water is unlikely to have negative effects on dieters, they can gain the same benefits by drinking regular water, do not need a recipe for sassy water from an expensive book in order to lose weight.) The four day anti-bloat jump start is very low in calories: if dieters can stick with it, they are likely to lose some weight.
Rapid weight loss at the outset works to motivate the dieter who is likely to continue following the plan and give it good reviews if they see results quickly. During the main phase of the diet, participants eat four, four-hundred calorie meals each day. Each meal contains a MUFA.
Critics of the Flat Belly Diet called the advice in the jumpstart plan pure speculation as there is not scientific evidence linking lack of sleep stress or monounsaturated fat consumption to reduction in belly fat. The cover of the book claims that followers can lose up to 15 pounds in 32 days: to do so, the average person would have to reduce their calorie intake by over 1,640 calories a day. Losing fat that rapidly is almost impossible; the weight lost by dieters in the beginning of the program is a loss of water.
What I found most troubling is that the authors make a lot of claims about MUFAs that might be true, but are not benefits limited to the intake of MUFAs specifically. For instance, the authors cite studies that show diets high in MUFAs protect heart health, ward off type two diabetes, cut metabolic syndrome risk, reduce inflammation, and lower your risk of breast cancer. A close reading for the claims in these sections show that diets with MUFAs might indeed be healthy, but other diets that are low in saturated fats and moderate in calories can provide the same benefits. In other words, MUFAs are a good part of a healthy diet but it is not necessarily any attribute in MUFAs that makes the diet beneficial.