Celebrities ranging from Katy Perry to Kelly Osbourne are touting the supposed benefits of the “M Plan,” a new fad diet whose proponents claim causes weight loss in exactly the places where women usually want to see it most – the thighs, hips and waist.

Like most fad diets, the eating plan is specific and rather silly: replace one meal per day with just mushrooms, continue this every day for two weeks, and watch the pounds melt away. However, also as with the vast majority of fad diets, health and nutrition experts are skeptical of the claims.

Adding to the skepticism, no one company, individual, or health professional seems to be taking credit for the development of the diet. A diet plan not created by a dietician or health expert should always be approached with an air of caution.

Mushrooms – Some Sort of Super-Vegetable?

Registered dietician Katherine Tallmadge says there’s nothing special about mushrooms in particular that would cause weight loss, and that replacing a meal that would normally contain larger amounts of calories, fat and carbs – say, fried chicken or fettuccine with meatballs – with any given vegetable would yield the same results, whether that vegetable is asparagus, carrots, or something else.

A better plan, of course, would be to replace one high-fat, high-calorie meal per day with one that includes only vegetables – but not just a single vegetable. By including a wide variety of vegetables such as broccoli, carrots, onions, peppers, squash and tomatoes, you’d get a much wider variety of vitamins and minerals, as well as a dish that tastes better. Serving these types of vegetables grilled over a protein-rich starch such as quinoa, for example, would make for a tasty and nutritious meal indeed.

The Myth of Targeted Weight Loss

But what about the M Plan’s claim that replacing one daily meal with mushrooms for two weeks will cause you to lose weight from your hips, waist and thighs, but not from your bust? Ridiculous, according to Tallmadge, who specifically says that no type of diet will allow you to lose weight from certain parts of your body but not from others. In fact, according to Yale Scientific and countless other expert publications, targeted weight loss is impossible even if you perform exercises that work out a particular area of the body. Performing crunches regularly will cause you to make gains in muscle mass, definition and toning in your abs, for example, but it won’t cause you to lose stomach fat any faster than you lose fat from your buttocks, thighs and neck.

Instead, Tallmadge says that the areas of your body that lose weight with exercise (or that gain weight with a lack of exercise and excessive caloric intake) are largely determined by your genetics. If your mother and father tend to gain weight in their midsections when they become inactive, for example, you probably will too.

Smoking habits, age and other factors play into this as well, according to Tallmadge. Evidence has shown that as women age, they become more likely to gain weight in their midsections due to hormonal changes. Smokers have also been shown to have a higher risk for gaining belly fat.

The Bottom Line

The M Plan, a new diet craze that asks participants to replace one meal per day with mushrooms and nothing but mushrooms, doesn’t hold up to scientific scrutiny. Although replacing one meal per day with mushrooms will likely result in reduced caloric intake and subsequent weight loss, a tastier and more nutritious plan would be to eat at least one vegetarian meal per day that includes a wider variety of vegetables.