Alina Petre, MS, RD is a registered dietitian with an expertise in sport nutrition. She completed her nutrition undergrad in Canada, received her master's degree in the United Kingdom. In this review, she suggests that the Fast Metabolism Diet can be effective for weight loss. However, Alina suggests that this diet is based on pseudoscience and lacks scientific evidence. Plus, the diet may be unsustainable and also restricts some beneficial foods.
Fast Metabolism Diet Review: Does It Work for Weight Loss?
Potential Downsides
The Fast Metabolism Diet has major drawbacks as well. Here are some of the most prominent.
Based on Pseudoscience
The Fast Metabolism Diet puts a strong emphasis on consuming specific foods in a certain order to boost metabolism and promote weight loss.
However, there is little scientific evidence backing such principles.
For instance, Phase 1 advocates a high-glycemic, carb-rich diet as a way to encourage your adrenal glands to produce fewer stress hormones and prepare your body for weight loss.
However, research shows that high intake of simple carbs may raise stress hormone levels — not diminish them (13).
Despite claims to the contrary, there is also no evidence that eating carb-rich foods for two days in a row will reduce stress and anxiety — or gird you for weight loss.
Phase 2 advocates for a high intake of protein and supposedly alkalizing vegetables as a way to build muscle, keep your pH in balance and help your liver release fat cells from storage.
High-protein diets are indeed linked to building muscle, especially when combined with resistance training. However, there is no evidence that vegetables are effective at treating an imbalanced blood pH (1, 14).
In fact, there is ample evidence that your body can naturally maintain blood pH within a strict range — regardless of what you eat. Furthermore, no studies suggest that alkalizing vegetables can stimulate your liver to release fat cells from storage (15, 16, 17).
Another main principle of the diet is that it will keep your metabolism stimulated, which will get it to work faster and burn more weight.
However, there is absolutely no research to support this theory of “surprising” your metabolism as a way to lose more weight.
Though some foods can cause slight increases in metabolism, any increase is minor and unlikely to help you lose a substantial amount of weight (18, 19, 20).
Finally, there is no evidence that this diet’s emphasis on organic foods and nitrate-free meats has any boosting effect on your liver’s ability to burn fat.
May Be Unsustainable
The Fast Metabolism Diet is frequently criticized for being unsustainable.
Many people complain that it requires too much measuring, weighing and food prepping to fit into a busy lifestyle.
Such a specific and restrictive diet may also be difficult to follow if you eat out regularly or attend barbecues, birthday parties or holiday events.
Restricts Some Beneficial Foods
Although the long list of foods to avoid does cull many processed foods from people’s diets, it also cuts out some beneficial ones.
For instance, soy is linked to a modest decrease in cholesterol levels and may also contain some cancer-fighting compounds (21, 22).
Caffeine is another banned food on this diet which is associated with improved brain function, protection against Alzheimer’s and Parkinson’s and a lower likelihood of depression (23, 24, 25, 26).
