The Evidence for Caloric Restriction: A Response to Dr. Fung’s CRaP

April 29th, 2017|Fat Loss, Nutrition|
The Evidence for Caloric Restriction - Myolean Fitness

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So a few weeks ago, we published an infographic which showed that all weight loss diets work through caloric restriction and, consequently, through the resulting caloric deficit.

A few people objected to it, saying that body composition and health are not just about a caloric deficit but, rather, also about food quality.

Here’s the thing: WE AGREE 100%!

We’ve actually gone out of our way several times in a few articles to make this point crystal clear. We even mentioned it in the first article we ever published, where we talked about the “secret” to fat loss.

The Evidence for Caloric Restriction - How Diets Work - Myolean Fitness

So no disagreement there. For optimal health and body composition, things like macronutrient amounts, fiber intake, food quality, meal timing and so on are important.

However, for a net increase or decrease in the body’s energy stores to take place, an imbalance between energy intake (from food) and energy output (from activity) must happen.

Practically speaking, for fat loss to occur, caloric restriction has to take place (or at least an increase in energy expenditure without a concomitant increase in caloric intake).

The above is something that is objectively true and which the entire scientific community agrees on, by the way.

Strangely enough, however, an obesity doctor seems to disagree.

A ranty post by an angry Doc

So a few days after the above infographic was published, Dr. Jason Fung (a nephrologist), responded with a ranty post on his blog (which you can read here) essentially claiming that caloric restriction doesn’t work for weight loss in the long term.

Now, if you manage to go through his entire article, you’ll notice that his argument essentially boils down to that caloric restriction doesn’t work for weight loss in the long term, despite people adhering to their diets. 

He even shares a couple of graphs from a few studies which show that, initially, weight loss occurs during calorically restricted diets, but then weight regain happens as weight slowly creeps back up during the months and years that follow.

Although Dr. Fung doesn’t offer an explanation as to why the weight is regained despite the subjects complying to their diets, he seems to suggest that this happens because of a decrease in energy expenditure.

Let’s not get ahead of ourselves, though. Let’s analyze Dr. Fung’s points one by one.

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Changes in metabolic rate with caloric restriction

After the first paragraph where Dr. Fung is just being sarcastic, he goes on to talk about energy balance and the First Law of Thermodynamics, essentially agreeing that it always holds true (phew).

He goes on to state that (and these are direct quotes, by the way):

  • “If you eat less (he means “fewer”) calories, you will burn less (*fewer). So there is no overall change in body fatness”

and that

  • “Basal metabolism may increase or decrease up to 40%.”

So are the above statements true?

Well, ish. It’s true that caloric restriction results in a decrease in energy expenditure and that hypercaloric diets result in an increase in energy expenditure. However, the statement that the basal metabolism (i.e. BMR/RMR) may increase or decrease by up to 40% is not supported by any scientific research. 

So how much does BMR/RMR increase/decrease with over- and underfeeding?

With regards to overfeeding, the largest BMR increase that we have found in studies lasting at least 2 weeks (and after adjusting for weight gain) is around 17% – i.e. nowhere near the 40% that Dr. Fung claims. Moreover, this scientific research paper suggests that the average BMR increase with overfeeding to be around 10%.

What happens to our metabolic rate with caloric restriction (underfeeding) then?

From what we could find, the largest drop in RMR in weight-stable conditions (and after adjusting for weight loss) was seen in the Minnesota Starvation Experiment, which recorded a (drumroll…) 15% drop in metabolic rate. Yep, still nowhere near the 40% which Dr. Fung claims. It’s also worth noting that this was a semi-starvation study, where subjects were in a severe caloric deficit until they reached around 4% body fat.

So where did Dr. Fung go wrong in his “calculations”? 

Well, Jason probably failed to consider that reductions in metabolic rate should account for weight loss or gain, since a smaller body will burn fewer calories and a larger body will burn more. So, when weight loss occurs, the honest thing to do is to compare the new BMR to the predicted new BMR (based on the reduced body weight) and not to the old one (i.e. before weight loss had occurred).

On a relevant note, as you can see in the table below, science has a pretty good idea about how much different components of the human body contribute towards the metabolic rate.

Dr. Fung’s CRaP

In the next paragraph, Dr. Fung continues with the sarcasm, referring to the approach of caloric restriction for weight loss as CRaP (Caloric Reduction as Primary).

If you delve a little more into it, you’ll notice that he is, essentially, making a number of assumptions on what he thinks researchers and fitness professionals think, and then basing his arguments on that.

More specifically, Dr. Fung thinks that we think that:

  • a change in one side of the energy balance doesn’t cause a change in the other
  • food intake is not affected by hunger, hedonic, sociocultural and other variables
  • exercise (or TEA) is a major component of total energy expenditure
  • the endocrine system is not involved in the regulation of adipose tissue

Hate to break it to you, Doc, but no one thinks that. At least no one with a relevant education, that is. 

Anyway, let’s move on.

Weight loss and long-term maintenance

So after a short attempt at “sciencing” for a while, Dr. Fung continues by asking the following question:

“So, where is the evidence that reducing calorie intake as the primary strategy results in long term meaningful weight loss?”

Well gee, Doc, we’re glad you asked!

This 10-year observational study of 2886 men and women found that, after 10 years, average weight loss with caloric restriction and an increase in activity was around 50 pounds.

The researchers reported that “decreases in leisure-time physical activity, dietary restraint, and frequency of self-weighing and increases in the percentage of energy intake from fat and disinhibition were associated with greater weight regain.”

Essentially, weight loss success in the long term was found to be associated with staying active, controlling caloric intake, keeping track of body weight and not eating huge amounts of fat.

The authors also reported that “long-term weight-loss maintenance is possible and requires sustained behavior change”.

Truly ground-breaking stuff. I guess common-sense advice doesn’t sell well, though.

Why do people regain lost weight?

Dr. Fung continues by presenting a couple of studies (along with a few graphs), which show that a large proportion of the weight lost by most subjects is regained in the years that follow.

Here’s the thing: we’re not saying that people always succeed in losing weight and keeping it off. Quite to the contrary. Most people seem to regain much of the lost weight after a few months and years.

Here’s where Dr. Fung is being brutally dishonest, however (or, at the very least, embarrassingly misinformed). He claims that, in those studies, weight regain happened despite subjects adhering to their diets.

Here are a couple of direct quotes from his article:

  • “In a pattern familiar to every person who has ever dieted, the weight starts to regain despite continued compliance to the diet”
  • “Also, it is important to note that women did, in fact, stick to their calorie reduced diet. Yet the weight regain still happened. BUT it wasn’t because of non compliance.”

Seriously, Doc? Are you going to stoop that low? Are you going to sit there and pretend as if you don’t know full well that weight regain happens exactly because of lower dietary adherence and poor compliance over time?

Tisk tisk, Doc.

Anyway, are you ready for some science? Yes? Awesome!

First and foremost, here is some research which compared different diets (Atkins, Ornish, Weight Watchers and Zone) and which found that adherence to caloric restriction (even when it’s self-reported) plummets over time.

Here’s one of our favorite quotes: “in the long run, sustained adherence to a diet rather than diet type was the key predictor of weight loss and cardiac risk factor reduction in our study.”


Here’s a table from the same study, showing that all diet interventions resulted in meaningful weight loss at the start, but weight regain slowly started to take place as the months passed, evidently because of lower dietary adherence.


Let’s see if you remember what you learned in statistics class, Doc. What does this next graph show? Do you, perhaps, see any statistically significant correlation between weight loss and dietary adherence? Well, you should, because there is one!


Ready for more? Great!

Here’s a recent meta-analysis which compared weight loss between low and high carbohydrate diets (and included 7286 individuals) and found no significant weight loss differences between the diets after 12 months.

The researchers concluded that: “significant weight loss was observed with any low-carbohydrate or low-fat diet. Weight loss differences between individual named diets were small. This supports the practice of recommending any diet that a patient will adhere to in order to lose weight.”

Here are a few more of our favorite quotes from the study:

“These findings support recent recommendations for weight loss in that most calorie-reducing diets result in clinically important weight loss as long as the diet is maintained”


“because different diets are variably tolerated by individuals, the ideal diet is the one that is best adhered to by individuals so that they can stay on the diet as long as possible.”

Notice a common pattern there? Yep, dietary adherence TRUMPS everything else.

Ah, yes. Science is awesome.

We won’t bore you with any more studies by the way. The above is a meta-analysis and is literally loaded with references you can check out yourself.

Conclusions and recommendations

So here are our conclusions and recommendations. Sadly, they are neither ground-breaking nor book-selling, but that’s life.

The focus of ANY weight loss intervention should be to create a caloric deficit with a diet that is:

  • composed primarily of minimally-processed, micronutrient dense foods
  • has enough protein to prevent losses in lean body mass
  • doesn’t create deficiencies in micronutrients
  • honors the individual’s personal preferences with regards to meal timing, food choice, and so on
  • can be adhered to in the long term
  • promotes a healthy relationship with food

NOW BUY OUR BOOK, DAMMIT! Ok ok, we don’t have one… yet.

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What next?

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  1. Carl Juneau, PhD 30/04/2017 at 11:25 pm - Reply

    Good one 🙂

    To be honest, as a researcher from another (related) field, this ongoing debate is hard to follow. Both sides (you and Dr. Fung in this case, but I’ve seen this with others) seem to cherry pick and construct straw man arguments.

    I’d rather not get into long debates, but here’s an example:

    You say he’s wrong to point out that calorie restriction failed, even if subjects adhered to their diet in the studies he’s cited. But you then cite other studies to support your point. Did you check the studies he’s cited?



    • Myolean Fitness 01/05/2017 at 1:11 pm - Reply

      Hey Carl,

      Thanks for your comment.

      Absolutely! I checked the studies Dr. Fung cited and could not find anything suggesting that researchers assessed dietary adherence. If you want to check yourself and don’t have access to the full-text articles, I’d be happy to send them!

  2. Justin 29/05/2017 at 7:48 pm - Reply

    Man this doc Fung is retarded. His comparison to kcal in & kcal out is like the earth isn’t round but its square.

    Wtf?? Not scientific proven just horseshit lmao

  3. Leslie 29/06/2017 at 12:20 am - Reply

    Intermittent fasting works best for people with insulin resistance. Yes obviously for someone who does not have insulin resistance who is overweight by eating too many calories can cut calories and access their stored fat easily making up for the missing energy from stored fat. This is why someone like Kim Kardashian can eat a 1700-1800 calorie diet and workout and consistently lose weight and keep it off. She is accessing her stored fat every day. For someone with insulin resistance, their bodies cannot access their stored fat, so the only way to maintain weight loss, they constantly have to lower their calorie intake to match their new metabolic rate in order to keep losing and maintain. This is a losing battle as eventually they would be eating nothing and starving.For example, if Kim had insulin resistance, she would probably have to lower her calorie intake to 1200 calories or less to get to 120 pounds and maintain at 1200 or less when she should have been able to achieve weight loss eating 1800 calories and maintaining around 1700. Fasting helps someone with insulin resistance to deplete their insulin so they can access their fat stores. Basically it is how they can cure insulin resistance and make their bodies like Kim Kardashian’s body. Yes they would have to eat a low carb diet to help lower insulin and create a calorie deficit by food or working out or both to acheive weight loss. The benefit is they would not have to eat less and less forever to maintain weight loss. Fasting will also work for people without insulin resistance. My guess is those are the people who lose 20 pounds in 1 month like some people boast 🙂

    • Myolean Fitness 29/06/2017 at 11:38 am - Reply

      Thanks for your comment, Leslie!

      I am not sure where exactly you are getting this information from… Mind sharing it with us?

  4. Betty 28/09/2017 at 4:50 pm - Reply

    I agree with all you have written. Perhaps Dr Fung meant as a person ages, he cant maintain weightloss if your hormones change, health issues change,etc,,? Certainly even if we do all the right things, if a dr put us on a medication that causes weight gain, that would also affect us.

    • Myolean Fitness 28/09/2017 at 7:03 pm - Reply

      Thanks for your message, Betty!

      Well, contrary to what most people think, age-related hormonal changes are more likely to affect where we store body fat than if and how much fat we store. It’s also worth noting that basal metabolic rate doesn’t drop much as we age. People usually gain weight mainly because they start becoming less active both in terms of exercise and in general day to day living (Non Exercise Activity Thermogenesis).

      Some of our postmenstrual clients have actually lost over 30 pounds and maintained it for 5+ years!

      With regards to medication, it can get pretty complicated, since some medication can cause massive increases in water weight, while some can cause feelings of tiredness and hunger. Depending on the situation, the gain in weight could be actual body fat or merely just water.

  5. Steve 28/09/2017 at 8:11 pm - Reply

    Author of The Case Against Sugar, Why We Get Fat and Good Calories, Bad Calories.

    If you have read these, where does this author fit into this discussion? Thanks

    • Myolean Fitness 29/09/2017 at 8:27 am - Reply

      Hey Steve, thanks for your comment.

      Gary Taubes is great at writing science fiction!

      On a serious note, Gary is a proponent of the CIM of obesity, which has been pretty much debunked in scientific research. Gary debated Alan Aragon at the Epic Fitness Summit in the UK a couple of years ago on this. This should make it clear how it went:

      Also, here’s a description of how the debate went by Ben Carpenter:

  6. Jo tB 29/09/2017 at 10:25 am - Reply

    I think both of you make valid points. However, it is not black and white: you lose weight or you don’t. I started putting on weight in my teens and have been “dieting” for over 50 years. In the beginning I dropped the weight effortlessly by dropping starches (potatos) and sugar out of my diet. After menopause I started to put the weight back on and no amount of cutting back on anything has shifted it. 17 years ago I was diagnosed as type 2 diabetic. Once again I started changing my diet in an effort to lose the weight and increase my insuline sensitivity, no avail. My body has a life of its own, and does the exact opposite of what is expected. What happens in most diets you drop things out without replacing them with other sources, creating deficits, whether they be calories, vitamins, nutrients. How does the body (i.e. your gut biome) react in a deficient state? It tries to compensate and get the deficiences back but from where? Apparently not from your fat stores. So how do I solve the problem in later life having jiggled with my metabolism for over 50 years? Not another diet apparently.

    • Myolean Fitness 29/09/2017 at 11:39 am - Reply

      You just haven’t found a good coach to help you with your weight loss goals yet!

      On a serious note, we’re aware of all the hormonal issues that accompany aging and menopause. Many times, the best solution is to see an endocrinologist to help you sort out your hormones before trying to lose weight.

  7. Rumi Nation 30/10/2017 at 4:13 pm - Reply

    you are essentially advocating the biggest loser diet of reduce calories and increase movement… while yes this works on the show and elsewhere do you ever wonder why there is no “biggest loser reunion?”

    its because they are all fat again! there in lies the mystery.

    • Myolean Fitness 30/10/2017 at 4:41 pm - Reply

      Thanks for your comment, Rumi.

      I recommend that you re-read the article, as it seems you have missed a few key points:

      – ALL diets work for weight loss through a caloric deficit. This includes low carb diets, low fat diets, intermittent fasting, etc.
      – The reason most people (including the Biggest Loser subjects) regain lost weight is simply because they fail to build the behaviors needed to adhere to their diets in the long term. This means that when they reach their goal, they simply revert back to their past behaviors – i.e. they eat too much and become much less active.

      The reason our clients ALWAYS manage to lose weight and keep it off is because we help them change their lifestyles instead of just forcing them to “eat less and move more”

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