Last updated:

25 July 2023

Thanks to the crazy world of social media, mono diets are an increasingly popular weight loss trend – and today I want to show you why it’s total bulls**t.

Reading time:

7 min read

So-called “mono diets” are sweeping social media at the moment.

It’s based upon the idea of eating one single food at every meal

So what type of food are we talking about here?

Well, that depends on who you follow. Some of these self-appointed “gurus” are saying you should eat just bananas, and others saying you should eat only potatoes, heck there are even brands which have built an entire business out of it (cabbage soup diet!).

The creators of this nonsense hail it as “the next big thing” in weight loss, but today “the mono diet” is gonna get wrecked.

I’m going to break down the science and show you why this is one trend you should AVOID.


When I was in college, a friend of mine got a job at the local Pizza Hut.

At first she loved getting free pizza every night, but it didn’t take long for the tables to turn…

  • Week 1 – Yesss! Pizza for dinner!
  • Week 2 – Okay, I’ll have some pizza.
  • Week 3 – Motherf**king pizza can f**k right off.

And that’s pizza, folks.

It’s probably the world’s nicest food, and a damn sight more appealing than the things you’ll be asked to eat on a traditional “mono diet”.

The cabbage soup diet is a good eample of this. As the title suggests, the goal is to spend a full month eating cabbage soup and nothing else.

F**k… I’d rather have my eyes poked out with a penis.

Research shows us that in order for a diet to be successful it must be sustainable, and one of the key reasons most mono diets FAIL is because they cannot clear this hurdle. (1)


When was the last time you ate turnip?


They’re rich in vitamin K, and your lack of eating them is probably why you bruise so easily.

Now imagine having a deficiency in every other vitamin and mineral too. You’d have crappy hair, oily skin, morning death breath, weak fingernails, annoying mood swings… the list goes on.

These are all very real dangers of a mono diet, because eating the same food over and over again means we are missing out on crucial micronutrients our body NEEDS.

(You can see a demo of this by breaking out a history book and looking up the lifestyle of sailors in the early 1900s; after spending months at sea eating only rice, they’d develop nasty conditions like scurvy.)

And then there’s protein

If you are training to build muscle you need to prioritize protein, but the majority of mono diets will not let you do this. That means it’s almost impossible to build muscle eating this way, because your body does not have the necessary nutrients it needs to recover from training. (2)


Like every other diet, success with a “mono diet” depends on calorie balance.

One of the main reasons people see results in the first two weeks with a mono diet is because when foods are so restricted we tend to dramatically reduce the number of overall calories we eat per day, and our body also flushes a f**k-tonne of water from our muscle cells.

This gives the illusion of fat loss.

Unfortunately what tends to happen after that is people get so frustrated they binge eat, and often wind up heavier than when they started.

This can lead people into a trap of bingeing and starving.

But the folks selling single food diets won’t even MENTION calorie balance. Instead, they’ll say you can only lose weight by avoiding certain food groups and sticking to the things on their pre-approved list…

That’s utter bulls**t.

You can lose weight in a whole variety of different ways – there’s no need to be scared of any particular food group! A study published in the American Journal of Clinical Nutrition showed that provided we control total calories (to control weight loss) and total protein (to support muscle growth), you can literally shuffle carbs and fats to suit your tastebuds and still lose the same amount of weight. (3)

Further research has since doubled-down on this, concluding that so long as total calories and total protein are controlled there is no significant difference in weight loss – regardless of the make-up of other macronutrients! (4, 5, 6, 7, 8)

So don’t let anybody tell oyu that you can’t eat carbs, or you can’t eat fat, or you have to eat only one food, etc.

In short it’s because people continue to fall for it.

For example, take a quick look at “Freelee The Banana Girl”.

This absolute nut-job wrote a book saying you should eat nothing but bananas – the worst part is it sold 3000 copies 24 hours, and her Instagram account grew to 300,000.

There are plenty more like this…

Another popular one food diet recommends eating nothing but carrots, as also have the Twinkie diet, and even the milk diet (by two “doctors”, no less!).

This haphazard style of eating has also spread to Hollywood…

Ashton Kutcher famously tried fruitarianism (a mono diet which limits food to only fruit) while preparing for his role as Steve Jobs. It left him hospitalized. Matt Damon also used a mono diet (this time eating only chicken) while preparing for his role in Courage Under Fire. He ditched the approach after his doctor warned he was in serious danger of causing permanent damage to his heart.

And then we have Gwyneth Paltrow

The Goop frontwoman is happy to jump on any fad diet trend in a bid to cream dollars from her fans, and back in 2017 she was telling new parents to go on a two week raw goat’s milk cleanse (?!).

datt damon chicken breast diet
Matt Damon at just 139lbs.

Every year it seems we have a new diet claiming to be the “next big thing”.

You’ll notice they often revolve around hailing certain food groups while demonizing others (protein makes you fat… carbs make you fat… fat makes you fat… etc.) and they often encourage you to buy their products for “faster results”.

The hard truth is that science disagrees.

The “best diet” is the diet you can stick to, and even the NHS agree with me on that.

Provided you stay within your daily calorie requirements and eat enough protein to support muscle growth, you can squeeze ANY FOOD into your daily diet without sacrificing results – and you can do it while simultaneously creating a much better relationship with food and without missing family occasions for fear of “cheating” on your diet!

The mono diet is a fast-track to an eating disorder.

I hope you enjoyed this breakdown.

Who Is Russ Howe PTI?


Russ has been a personal trainer in the UK since 2002, and provided both training advice and full programs on this website since 2011.

His work has been featured in Men’s Fitness magazine, and the content on this website led to him being voted one of the world’s top 50 fat loss coaches by HuffPost.

Russ’ days are spent coaching men and women in the legendary Powerhouse Gym, and creating new content for the 109,246 followers of his popular free weekly e-mail, which you can join below!


  1. Stewart T. M., et al. Rigid vs. flexible dieting: association with eating disorder symptoms in nonobese women. Appetite (2002).
  2. Morton R. W., et al. A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults. Br J Sports Med (2018).
  3. Leibel R. L., et al. Energy intake required to maintain body weight is not affected by wide variation in diet composition. Am J Clin Nutr (1992).
  4. Golay A., et al. Similar weight loss with low- or high-carbohydrate diets. Am J Clin Nutr (1996).
  5. Golay A., et al. Weight-loss with low or high carbohydrate diet. Int J Obes Relat Metab Disord (1996).
  6. Luscombe-Marsh N.D., et al. Carbohydrate-restricted diets high in either monounsaturated fat or protein are equally effective at promoting fat loss and improving blood lipids. Am J Clin Nutr (2005).
  7. Raatz S. K., et al. Reduced Glycemic Index and Glycemic Load Diets Do Not Increase the Effects of Energy Restriction on Weight Loss and Insulin Sensitivity in Obese Men and Women. J Nut (2005).
  8. Johnston C. S., et al. Ketogenic low-carbohydrate diets have no metabolic advantage over nonketogenic low-carbohydrate diets. Am J Clin Nutr (2006).

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