The Cruel Hoax of the Low Fat Diet – Calories Part IX

By Jason Fung, MD

Click here for Calories Part IPart IIPart IIIPart IVPart VPart VIPart VII, and Part VIII. How can we lose weight? We all think the caloric reduction is the key, but so far, it doesn’t seem to be working. Here’s our conventional view of obesity…

Let’s now see what happens in the real world. Can we actually lose weight by eating less and exercising more? For that we can look at the gigantic Women’s Health Initiative study.

Women’s Health Initiative

Low-fat dietary pattern and weight change over 7 years: the Women’s Health Initiative Dietary Modification Trial
Howard BV et al. JAMA 2006; 295:39-49

This was a massive, expensive and ambitious National Institute for Health study published in 2006. It also set the bar for awesomeness. Close to 50,000 women were recruited for this randomized controlled trial. This is the absolute gold standard in experimental medicine, and this study is probably one of the most important studies of its kind.

There was an average follow up of 7.5 years. 19,541 women were randomized to the study diet. These women had a series of education sessions to reduce fat to 20% of daily calories, increase vegetables and fruit to 5 servings/day, and grains to 6 servings/day.

There were 18 session in the first 12 months, group activities, individual interviews with reflective listening, targetted message campaigns and personalized feedback.

This was consistent with the nutritional recommendations of the time which enrolled women from 1993-1998. Looking at the graph to the right, it appears that the dietary counselling was quite successful in changing behavior. Total caloric intake reduced from 1788 to 1446 calories/day – a reduction of 361.4 calories/day for over 7 years. Total awesomeness!


Fat as a percentage of calories reduced from 38.8% to 29.8%. Carbohydrates increased from 44.5% to 52.7% since whole grains were encouraged. It was emphasized that the main goal was to reduce fat as a percentage of calories and not weight loss per se.

Exercise was also encouraged. As you can see, the women increased their daily physical activity increased from 10 METs/wk to 11.4 METs/wk. MET is simply a measure of physical activity. In other words physical activity increased 14% over baseline over those 7.5 years.

The control group, by contrast just got a copy of Dietary Guidelines for Americans but had no other contact with the study dieticians.

The study group successfully followed a lower calorie, lower fat diet while simultaneously increase exercise (Eat Less, Move More). Average weight at the beginning of the study was 76.8kg (169 lbs) with an average Body Mass Index of 29.1. That puts them in the Overweight (BMI 25-29.9) category but bordering on the Obese category (>30). So what happened?


The Eat Less, Move More group starts out great with an average of more than 2kg over the first year. By the second year, the weight starts to be regained and by the end of the study, it is clear that there is no significant difference between the two groups.

Reducing calories by 361 calories/day every day for 7 1/2 years and increasing exercise by 14% did not result in any more weight loss than doing nothing.

You might think that these women replaced some of their fat with muscle. Unfortunately, there was also no difference in their waist circumference or the Waist-Hip Ratio (WHR).

Weight loss over 7.5 years of the Eat Less, Move More strategy was not even one single kg (2.2 lbs).

What is still worse is that over 7.5 years the average waist increased from 89.0 to 90.1 cm, and the average WHR increased from 0.82 to 0.83. This indicates that not only did these women not lose weight, they were actually fatter than before.

I have treated many patients who say to me “I don’t understand. I eat less. I exercise more. But I can’t seem to lose any weight.” I know. I believe them. Because this advice to has been proven to failDo caloric reduction diets work in the real world? Absolutely not.

This then is The Cruel Hoax of the Low Fat, Low Calorie Diet that we have all be told to follow. It. Just. Does. Not. Work. Eating less does not result in weight loss. It is cruel because so many of us have believed in it. It is cruel because all of our ‘trusted health sources’ tell us it is true. It is cruel because when it fails, we blame ourselves. We need to throw this theory into the garbage where it belongs.

Let me state it as plainly as I can. Eating too much does not cause obesity. Exercising too little does not cause obesity. Therefore, eating less and moving more will not cure obesity. It is proven. Accept it.

Let’s recap what we know so far.

1. Our conventional view of obesity stems from the Caloric Reduction as Primary model. However, conclusive evidence shows that following a calorie reduced low fat diet will not result in any weight loss. It is likely that this model is completely wrong.

2. The body acts as a thermostat, not a scale. There is a certain Body Set Weight (BSW). Attempts to drop your weight below the BSW will result in activation of mechanisms to regain that weight. This includes increased hunger and decreased total energy expenditure (TEE).

So how can we lose weight? We need a new theory of obesity that explains how we get fat. What causes obesity? What is the aetiology of obesity? We need to understand the causes of obesity before we can figure out a treatment for it. What regulates BSW? Does overeating cause obesity?

Patience, we will get there…

Continue to Calories Part X here
Begin here with Calories I
See the entire lecture here: The Aetiology of Obesity 1/6 – A New Hope

By The Fasting Method

For many health reasons, losing weight is important. It can improve your blood sugars, blood pressure and metabolic health, lowering your risk of heart disease, stroke and cancer. But it’s not easy. That’s where we can help.

Jason Fung, MD

By Jason Fung, MD

Jason Fung, M.D., is a Toronto-based nephrologist (kidney specialist) and a world leading expert in intermittent fasting and low-carb diets.

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