Disclaimer: This blog post is my opinion. As with all of my diet reviews, the purpose of it is to examine the claims that the diet makes against the laws of physiology as well as the latest research. 

I’ve had a few requests to review the Fast Metabolism Diet, and once I took a two second look at the website, I immediately knew that I had found my next Diet Review. Hey, the author of the diet calls herself ‘The Metabolism Whisperer’! Can she actually coax unruly metabolisms into submission?  I needed to see this, most definitely. This review applies not only to this particular diet, but to most ‘metabolism diets’.

(Read my review of the Metabolic Renewal program here)

What is the Fast Metabolism Diet?

At first glimpse of the website, it’s apparent that the Fast Metabolism Diet is only a small part of what’s essentially a library of diet books by the same author. Not only that, but there’s a supermarket-sized offering of Metabolism branded pills, bars, shakes, audio books, digital books, apps, baking mixes, Metabolism spinach fettuccini noodles ($35.00 for a 12-pack..get ‘em while they last), and basically anything else you could want.

I’m sort of shocked that I couldn’t find a snow brush for my car or a couple of throw pillows on there as well. Maybe those are coming soon! 

Anyhow, I know that for many people, metabolism seems complicated. It’s actually not all that bad once you have the details broken down for you, and when you do, you’ll figure out that diets like this one that claim to speed up metabolism, are largely garbage.

Yes, I’m going there. Is it too early to make that statement?

Here’s the basics of what you should understand about metabolism:

  • Your metabolism is essentially how your body turns what you eat and drink into energy.
  • The only thing that we know of that really speeds up metabolism for the long-term is exercise. The more lean body mass (otherwise known as muscle) you have, the more calories you’ll burn at rest (aka increased BMR). 
  • Things that affect metabolism speed include: genetics, age, muscle mass, medications, caloric intake, hormones (especially thyroid hormones), body size, sleep patterns, and possibly gut bacteria. Diets – especially really low calorie ones – slow metabolism to conserve energy – it’s an adaptive measure that we’re born with so we don’t starve to death. 
  • I wrote an in-depth post about metabolism here. You can read it for more information about how your metabolism works (and doesn’t work), especially in relation to weight. 

The Claims of the Fast Metabolism Diet

When someone comes along and touts a ‘metabolism changing’ diet with detoxes, cleanses, and a boatload of metabolism-boosting supplement$, I immediately smell BS. When she writes 4+ books on the same subject, I wonder why the first one wasn’t effective enough that she needed to write three more.

When that person also poses on her website wearing a lab coat (for no apparent reason, but lab coats say you mean business, right?), and has been known to promote crazy unsubstantiated-by-science things like ‘fat burning foods’, I need to raise an eyebrow.

When I find that she has a degree in agricultural and animal science and then some education in homeopathy aka pseudoscience, I start nodding my head as in, ‘ahhh, I get this now’. But wait! She’s Hollywood’s ‘top nutrition guru’, which says a lot. Or wait. Hm. 

I know that I should keep an open mind to other healthcare disciplines, and I am sure that the author has helped many people in her own way. But seeing someone promoting patently false and overreaching claims and using them to sell all sorts of useless but expensive stuff makes me upset. I feel like vulnerable people are being taken advantage of, and that’s not okay. 

The Fast Metabolism Diet tells us that “food is not the enemy but rather the medicine and the fuel needed to rev-up our sluggish, broken-down metabolisms and turn our bodies into fat-burning machines.” 

And my favorite, “this is the silver bullet for anyone who wants to naturally and safely eat their way to a skinnier, healthier self.”

Translation: this is a fast, effortless way to eat and be skinny, which automatically means healthy. It’s all natural, except for the piles of supplements you need to consume on this plan (but I digress…more on that later).

And can we please refrain from ever using the word ‘skinny’ as if it’s some sort of desirable way of being? 

The Fast Metabolism Program

The Fast Metabolism Diet is a 28-day plan that has a rotation of three phases. Basically, the author claims that eating the right foods at the right time can ‘trick’ your metabolism into speeding up.

In her own words, “Each Phase focuses on different whole, healthy foods to calm your adrenal glands, reduce stress on your liver, and feed your thyroid so it can produce the hormones T3 and T4, the superstars of a fast metabolism.

You’ll reduce stress, too—and as a result, put the damper on the belly-fat hormone, cortisol. By keeping your metabolism guessing, you’ll get it working faster.”

Hint: your metabolism doesn’t ‘guess’ anything. Stop personifying bodily functions.


There are a lot of rules on The Fast Metabolism Diet. Here they are:

1. You must eat five times per day

2. You must eat every three to four hours except when sleeping

3. you must eat within 30 minutes of waking

4. You must stay on the plan for the full 28 days (keep repeating if needed until you reach your      target weight, then repeat either full 4 weeks every 6 months or 1 week every month)

5. You must stick to the foods allowed in the phase

6. You must follow the phases in order

7. You must drink half your body weight in ounces of water every day

8. Eat organic whenever possible

9. Meats must be nitrate-free

10. Exercise according to your phase

11. No wheat (excepting sprouted or natural yeast wheat)

12. No corn

13. No dairy

14. No soy

15. No refined sugar

16. No caffeine (or alcohol)

17. No dried fruit or fruit juices

18. No artificial sweeteners or fat-free diet foods

Keep in mind that after the 28 days, she recommends that you continue to avoid corn, soy, sugar, and caffeine except for ‘special occasions’

The phases and their ‘rules’ are as follows:

Phase 1: ‘Unwind’ days 1-2: 

This phase consists on high-glycemic, moderate protein, and low fat foods to ‘calm the adrenals’. I’ve never seen a diet that encourages high-glycemic foods as a rule, but alright then.

No nuts are allowed in this phase. ALL FATS are to be avoided. 

Phase 2: ‘Unlock’ days 3-4:

This phase is supposed to ‘unlock stored fat’ and build muscle. 

It allows only high protein, low carb, and low fat foods. It’s basically proteins and ‘alkalizing’ vegetables, but not no beets, carrots, peas, pumpkin, sprouts, sweet potatoes, tomatoes, turnips, squash or zucchini. What the eff did zucchini ever do to anyone? You’re also not allowed any grains or fruit.

No nuts are allowed on this phase.

Phase 3: ‘Unleash’ days 5-7:

In this phase, your metabolism is supposed to come roaring out of hibernation to burn all your fat! Exciting!! This phase is high in healthy fats, moderate carbs and proteins, and allows only low-glycemic fruit. It also includes ‘Thyroid-stimulating foods such as seaweed, coconut oil, shrimp, and lobster’

The portion sizes of food vary by phase and by amount of weight you want to lose. 

Let me put this out there RIGHT NOW because I’m already tired of this BS: 


Nowhere in the world is there research that tells us it’s beneficial to ‘surprise’ our metabolism and ‘keep it guessing’. Your metabolism does NOT work like that. It doesn’t have a brain, it doesn’t like playing games, it doesn’t guess anything. 

The only thing your thyroid needs to be ‘fed’ is iodine. If you live in a first-world country and have a varied diet, it’s unlikely that you’re iodine deficient. Also: coconut oil doesn’t stimulate your thyroid any more than Big Macs do. 

How can being on a diet ‘reduce stress’? Think about that for a second, will you?

T3 and T4 are thyroid hormones, as outlined in my Learning Curve post about your thyroid (here). There is no reason to take thyroid hormones or worry about them unless you’ve been diagnosed with a thyroid issue.

Also, the T3/T4 combination that many alternative healthcare practitioners sell (it’s available as part of this diet too, $HOCKER) has not been proven to be more effective than the T3 that is prescribed by physicians.

Supplements are not as tightly regulated as actual medications, so it’s anyone’s guess if what you’re buying is actually as effective as it claims. If you’re messing with your thyroid, don’t do it with some random ‘natural’ pills you found on the internet. That can cause you a world of trouble. 

There are no foods that can speed up your metabolism enough to burn fat. The thermic effect of food exists, yes – but the amount of calories you burn while digesting a chicken breast or a mouthful of chili peppers doesn’t make you lose weight.

There are no fat-burning foods. You can’t switch your metabolism off and on and off and on like a light.

You are okay. You’re going to be okay, without the Fast Metabolism Diet, so don’t go there. And if you do, the reason why you’re losing weight probably has nothing to do with your metabolism. It’s because you’re so restricted with what and how much you can eat. 

I would be remiss if I didn’t bring up the fact that soy is a big ‘no no’ on this diet, but then the author recommends that vegans following the diet eat tempeh and tofu…pure soy. Nonsensical.

Oh, and no wheat – but you can have spelt. Spelt actually is wheat. Hello?! I think she’s going for inclu$ivity here…cutting out vegans from this diet means less money for her, so she’s going to bend the rules for them. Nice! 

This is a low calorie diet that forces you to cut out a lot of foods. I mean, if you can’t eat corn and soy, you’re basically cutting out every single ultra-processed food. But instead of admitting that this is why you’re actually losing weight, the author has to lead you down the garden path using her crazy ‘metabolism’ claims.

Sadly, I read several variations on the following in some of the reviews: “The facts and science seem sound, although I have not researched them to be sure they are accurate, they make a lot of sense.”

NOOOOOOOO!! No they don’t! But what does make sense is why the diet industry still exists when people don’t do more research about what diets they’re using. 

The Upsells:

I know I just spilled the entire can of beans about the diet, but I still want to talk about the upsells – because the Fast Metabolism Diet seems to win the upsell award and to be honest, I feel that this destroys the diet’s credibility even further.

As I mentioned before, The Fast Metabolism Diet has a veritable smorgasbord of cleanses (lose 5 pounds in 5 days…their words, not mine) and supplements, paid support groups, pre-fab programs that promise to shed pounds in ridiculously short amounts of time with shakes and pills, and ‘bundles’ of supplements that promise to work in synergy – like the ‘Bye Bye Belly Fat’ bundle. 


A lot of the supplements offered in the store are based on imaginary conditions (Candida, I’m looking at you), or have little to no evidence behind their components.

Take the ‘Metabolism Control’ supplement, devised to ‘help you take control of your inner body’ (huh?) and decrease appetite. There’s nothing about vitamin B6, vitamin C, and chromium, random amino acids, and 5-HTP that has been proven to do anything significant for appetite reduction. 

The Metabolism Energy supplement (it’s annoying how every single one of her products starts with the word ‘metabolism’, but I digress) states that there’s Nobel Prize-winning research (this) proving that nitric oxide moves more blood and oxygen throughout your body. Okay, fine.

The author extrapolates this research finding for her own benefit, saying “The extra blood flow helps to remove waste products more efficiently out of fat cells to be burned for fuel.” 

Certainly, increased blood flow through the body may speed up some processes, but to carry that so far as to say that it will help you lose weight is completely made up and not evidence-based at all. They’re seriously making people pay $57.00 for 8.5oz of this stuff,  based on a shitty extrapolation that’s straight from the author’s imagination. Crazy.

I couldn’t find one single research study confirming that nitric oxide or arginine helps people lose weight in this manner. I actually did find studies on just arginine and weight, but they were mostly on rats and pigs. Those are not studies that I accept as proof of a similar outcome in humans.

Sorry. The one human study I found was poorly done, small, and short. Nope. 

There’s a pattern I see with all of the offerings in the Fast Metabolism Diet online store. They’re also exorbitantly priced, but it seems as though everything about The Fast Metabolism Diet is a money grab. It follows the the typical script:

  1. Make people feel as though they have more issues than they really do.
  2. Sell them a ‘solution’ using science-y language they don’t understand. 

It’s the MO of almost every diet program out there, and it’s really sad. You completely do not need a ‘Metabolism Colon’ supplement (inset eyeroll here) or probably 99.9% of the stuff in that store. What also irks me is that on every single page of the Fast Metabolism site, there’s a ‘buy now!’ popup, or some sort of product or service being sold. It comes off as completely disingenuous and gross. 

A Dietitian’s Take on the Fast Metabolism Diet

This is a low calorie diet, period. The phases don’t make any physiological sense, and the elimination of caffeine, wheat, soy, corn, and everything else for the short and long term doesn’t fix anything. It just makes more junk food off limits, and life a lot more annoying and less fun. No thanks.

The author of this diet is a proponent of homeopathy, otherwise known as ‘the air guitar of medicine’.

This does not mean that nothing she says is credible, but it does explain in part why this diet is essentially based on far-fetched and unproven claims. Take responsibility to research diets before you start them. I guess that’s why you’re here, though. Good job!

Working as a nutritionist in Hollywood doesn’t earn you any points. Everybody knows that stars do crazy diets that aren’t credible or applicable to your real life.

There are a lot of money grabs that you shouldn’t fall for. You don’t need to cleanse or detox your body AT ALL. EVER. Why am I still trying to defend this concept? Also, losing weight shouldn’t cost a ton of money. Stop!!

I don’t think this diet is dangerous in any physical way, but why would you ever throw money at something like this?

Hard pass.