Diet Wars

By Jason Fung, MD

The Diet Wars – to see whose cuisine reigns supreme – has been going on for some time. The incumbent, and increasingly looking-really-old-fashioned Low Fat diet has been recommended for many decades by most health professionals. It made its first appearance in the late 1970’s based on its supposed benefit for reducing heart disease. Dietary fat will clog your arteries! was the battle cry. Health professionals like doctors rallied behind the great Empire of Low Fat. But in a galaxy far, far away, a small Low Carb rebel band was forming to challenge this dietary orthodoxy, and embraced natural fats believing instead the culprit was sugar and refined grains.

The Empire put its prodigious resources into a massive ‘Death Star’ study that would prove the Low Fat paradigm for once and for all. Once this was completed, they believed, it could blast any rebel strongholds at will. The resulting Women’s Health Initiative (WHI), recruited close to 50,000 women into a ginormous randomized controlled trail lasting over 8 years. Women were randomly assigned to their usual diet group or a low fat diet. After 8.1 years, researchers would find, lo and behold, that these Low-Fat women would have less heart disease, less obesity, and less cancer. Ummm. Right. That’s exactly what DIDN’T happen.
Published in 2006, the WHI showed that following the low fat diet for 8 years, compared to eating the usual diet, did NOT reduce heart disease. It  did NOT reduce colo-rectal cancer. It did NOT reduce breast cancer. Despite reducing calories, it did NOT reduce weight either. That massive ‘Death Star’ study? Yeah, it just got blown to pieces. While the Low Fat dogma took a beating, but the Low Fat Empire, with its calorie restriction still limped on, trying to become the First Order.
Many of the formerly ‘crazy’ beliefs of the Low Carb Rebel band have been accepted into dietary orthodoxy. For example, few people believe that eating white bread, pasta, or sugar is all that slimming. Yet the original Food Pyramid exhorted Americans to eat 6-7 servings of bread daily. Where high fat foods like olive oil, avocados, fatty fish and nuts were shunned a mere 10 years ago, there is growing acceptance of these ‘healthy fat’ foods. Ten years ago, the term ‘healthy fat’ did not exist, because it was ‘well known’ that all dietary fats would kill you.

The latest battleground in The Diet Wars is the most recent study that just got published in the Journal of the American Medical Association comparing the Low Fat diet to the Low Carb diet. The details are well covered in this article, since the study itself is pay-walled (you need to buy it). As background information, I’ve written in many posts here that calories are not the major cause of obesity. Instead, it is a hormonal imbalance, predominantly of insulin, but also cortisol.
If this theory is correct, then giving insulin or cortisol will cause obesity. And guess what? It does. This is the Hormonal Obesity Theory, as opposed to the Caloric Theory, which holds that excess calories is the cause of obesity. If the calorie theory is correct, then reducing calories will cause weight loss. This has been tried millions of times over the last 50 years to absolutely stunning failure. No diet fails quite so spectacularly as the caloric restriction diet.

There is, of course, an overlap between the insulin stimulating effect of food and the caloric value. All normal foods increase insulin to some degree, unless you eat pure fat. Since most people don’t drink a cup of olive oil for dinner, we can safely assume that most people eat meals that have some combination of carbohydrates, proteins and fat. Thus all foods increase insulin to some degree, but some will raise it more than others. That simply implies that some foods are more fattening than others, even if exactly the same number of calories. This is just pure common sense and exactly what your grandmother would have told you, after chastising you for having no brains. Except for academic obesity specialists and researchers, who is foolish enough to think that 100 calories of brownies is equally fattening as 100 calories of kale salad? The calorie hypothesis – it’s a trap!

Insulin is one of the main drivers of obesity, leading to the Carbohydrate Insulin Hypothesis (CIH). This holds that dietary carbohydrates are the main or only cause of increased insulin, and thus reducing carbohydrate intake is necessary to lose weight. However, the CIH is incomplete, because there are many, many different influences upon insulin levels other than carbohydrates, including meal timing (eating late at night releases more insulin, incretins, vinegar, fibre all reduce insulin, insulin resistance and fructose directly increase insulin etc). This leads to a far more complete theory of obesity that takes all these factors into account instead of merely the carbohydrate or calorie content of foods.

With that background, I suggested in The Obesity Code that the main steps to reducing obesity are:

  1. Reduce your consumption of added sugars.
  2. Reduced your consumption of refined grains.
  3. Moderate your protein intake.
  4. Increase your consumption of natural fats.
  5. Increase your consumption of fiber and vinegar.

But above all else my main advice is to  eat unprocessed real food. Processed grains are not good, but neither is processed fats such as seed oils or processed red meats.

OK. Good. Now onto the study where they compared two groups – Healthy Low Fat (HLF) and Healthy Low Carb (HLC). The ‘Healthy’ part applied to both groups included instructions to:

  1. Maximize vegetable intake
  2. Minimize intake of added sugars, refined flours and trans fats
  3. Focus on whole foods

Other than the part about eating natural fats, it’s virtually identical to the advice we give in our Intensive Dietary Management program. Patients attended instructional sessions for the diet over the period of 1 year. In addition to the above advice, the Low Fat group restricted dietary fat to 20g/day and the Low Carb group restricted carbs to 20g/day. Participants then gradually added back fat or carbs to the lowest level they believed they could sustain. Yes, this part is not very rigorous, but it’s what happens in real life. Deal with.

As you can see, the dietary instructions worked pretty much as planned. There was no instructions given for caloric intake, tacitly acknowledging the complete futility of calorie counting as a useful dietary tool. Patients should eat until hunger is sated, no matter how much they ate. Nevertheless, both groups reduced their calorie intake from roughly 2200 cal/day to 1700 cal/day with no difference between groups.
This underscores that it is likely the intervention applied to BOTH groups that caused this caloric reduction. When you eat real food, you activate natural satiety mechanisms – cholecystokinin, peptide YY, stretch receptors in the stomach, incretins etc. that signal us to stop eating. But this applies to both low fat and low carbohydrate foods. When you eat processed grains (donuts) you don’t get full. When you eat unprocessed carbs (beans) you do. Thus you stop eating because you are not hungry at a level that is far below the previous caloric intake (roughly 500 calories/day). But it did not require calorie counting to achieve this. It requires cutting out all processed foods.
Was there any difference between the Low Fat and Low Carb groups in terms of weight lost? Yes and no. The HLF group lost 5.3 kg and the HLC lost 6.0 kg, not a statistically significant difference, but in Body Mass Index the HLF group lost 1.75 and HLC 2.07, which is statistically significant. There were no other important differences. Metabolic rate was similar in both groups.

There was also some huge differences between people in the same diet. In both groups, some people lost 25 kg (over 50 pounds) and some gained 10 pounds. ON THE SAME DIET! This shows the significance of one of the other importance of one of the IDMP’s main ‘rules’. Do what works for you.
We are not dogmatic about what diet to follow. If you follow a low fat diet and lose weight, great. The only logical thing is to keep doing it. BUT. If it does not work, then change it and see if it works better. The general rules are all the same – avoid processed foods, avoid added sugar, avoid refined grains, but you can tweak endlessly around the edges. The only thing that really matters to us is that you get results. Look, we are all individuals. I am good at medical physiology and suck at basketball. LeBron James is good at basketball and probably sucks at medical physiology. I make a living doing what I do, and he makes a living doing what he does. So why force one dietary approach to fit all?
So, call this a tie, although you could argue it’s a win for the Low Carb rebel band based on the BMI. So, why do I usually recommend a Low Carb diet? For several reasons. First, most carbs in Western society are refined grains. So Low Carb is a useful short hand for reducing sugar and refined grains. Secondly, Dr. Eenfeldt at www.DietDoctor.com smartly points out that if you consider all the Low Fat vs Low Carb studies (58 in total), Low Carb comes out on top 29 times and tied 29 times.  The Low Fat diet came out on top a grand total of 0 (zero) times. Yes. Zero times. This clearly favour the Low Carb rebel band. Anyways, would you bet on a team that wins 29 and loses 0, or the one that wins 0 and loses 29?
There are several key takeaway messages. First it reinforces the uselessness of the counting calorie approach. Second, by adopting generally agreed upon ‘Healthy’ eating patterns gets you most of the way to target. Third, it’s arguable that the Low Carb approach was better, but with all the differences between individuals, you really need to be open minded. Eating whole unprocessed carbohydrates might work for you. But eating all meat may also work for you. I care more about people getting healthy than being right. At IDM, we don’t tell people what they ‘must’ eat. There is no such thing. We see what they eat, and see if they get the results they are looking for. If it works, great. If it doesn’t work, then we change.

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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