Diet trends seem to work like revolving doors: each one jockeys for a slot in the collective health consciousness, only to be ousted in a matter of weeks or months. The latest in celebrity diets is the mushroom diet, or “M-Plan” as it is so cryptically titled, but experts raise an eyebrow at its claims to spot-reduce body fat at the dieter’s will.

Celebrities such as Kelly Osbourne and Katy Perry have adopted forms of the M-Plan, which encourages dieters to swap out their typical lunch and dinner with a mushroom-centric dish instead. The low-calorie, high-protein food offers a raft of health benefits, but it may be no different in fat-burning ability than traditional methods of weight loss that dictate the number of calories consumed must be less than the calories burned. The M-Plan professes weight loss within two weeks of its adoption.

“The diet is simply a low-calorie diet,” Tanya Zuckerbrot, a registered dietitian, told ABC News, noting that swapping a cheeseburger for a portabella burger will save you around 173 calories and, compounded over the 14-day period that the M-Plan recommends, will help a person lose weight. However, “fat is fat and no diet can actually help you spot reduce," Zuckerbrot said.

One of the benefits touted by the M-Plan is its unique ability to shrink a person’s thighs but maintain her breasts, or trim a waistline but keep a set of curvy hips. “The mushroom diet, just like the fungi itself, means you keep the weight where you want it up top and shed pounds where you don’t down below!” remarked women’s nutritionist and health broadcaster, Jeannette Jackson, to the Daily Mail.

Jackson highlighted the food’s natural benefits, which include improved bowel function from the hearty sources of fiber, and healthier skin, hair, and nails from the B vitamins, iron, and zinc.

'The dietary fiber in mushrooms helps promote good bowel function leaving you feeling more satisfied, so you won’t be hungry again as quickly, preventing you from snacking,” she told the Daily Mail. “Mushrooms are also extremely rich in protein – an ideal nutritional food source yet the vegetable is low in calories, which is important where weight loss is considered.”

“There’s a myth that the waist is the last area of the body where women lose weight. In fact, it’s one of the areas of the body that we move the most along with bums, thighs and upper arms,” she continued.

Zuckerbrot upheld Jackson’s praise of the food, as mushrooms no doubt offer a wealth of benefits that keep a person’s body and mind functioning more efficiently. Spot-reducing claims are another matter, as the body cannot discriminate in how it burns fat simply by the food it breaks down.

“Mushrooms are an amazing food. One cup has only 25 calories and 2 grams of fiber. They are also a great source of potassium; 1 cup of mushrooms contains more potassium than a banana or a glass or orange juice,” Zuckerbrot remarked, noting that however much weight a person loses, “the fact remains that no food in particular can create targeted weight loss.”

Her complaints are not rooted in speculation or opinion, she argues, but simply the science behind how the body processes food.

“Whether its mushroom or steak,” she said, “the laws of thermodynamics dictate, if you consume less calories, you will lose weight, just not everywhere but your breasts.”