Hormones are the key to weight loss, not calorie counting
- While the Calories In, Calories Out theory of weight loss sounds correct, it is flawed by incorrect hidden assumptions.
- Body fat stores, a very important determinant of survival, is very tightly regulated by our hormones.
- The Eat Less, Move More strategy of weight loss fails to address the underlying hormonal determinants of body fat storage, and ultimately fails for both long term weight loss and improved health.
By Jason Fung, M.D., Co-founder of The Fasting Method
Here are some key but false assumptions in Eat Less, Move More strategy of weight loss.
But what regulates how much body fat we carry? Are calories in excess of our metabolic needs simply dumped into fat stores like doorknobs into a sack without any type of regulation? Hardly. Nothing in human physiology works like that. Nothing.
Fat stores are hormonally regulated
The Energy Balance Equation is usually stated as:
Body Fat = Calories In – Calories Out
This is always true, but almost always misinterpreted to mean that if we simply eat a few less calories, we will lose body fat, ie. the Eat Less, Move More strategy of weight loss (I also call this the Caloric Reduction as Primary strategy). But there are three variables here –
- Body Fat
- ‘Calories In’
- ‘Calories Out’
If you change one variable, ‘Calories In’, then either Body Fat or ‘Calories Out’ may change to keep the equation stable. Many people ask us to assume ‘Calories Out’ is an independent variable and stays constant, which is simply not true. Further, it also assumes that body fat is simply an unregulated receptacle for excess calories. A landfill of excess calories if you will.
All human body systems are tightly regulated in order for us, as highly complex animals with many interdependent organ systems, to survive. This applies to every part of human physiology. For instance, height is tightly regulated by growth hormone. Blood sugars are tightly regulated by insulin and glucagon, among others. Sex differences are tightly regulated by testosterone and estrogen. Bone turnover is tightly regulated by parathyroid hormone. It goes on and on. Any bodily function you can imagine is under some regulatory system – usually hormonal (endocrine, paracrine, autocrine etc.).
Yet, body fat is a physiologically unique exception to this rule? That growth of fat cells is essentially unregulated? That the simple act of eating, without any interference from other hormones will result in fat storage? The extra calories are dumped into fat the same way one would dump a few leftover potatoes into a sack. These sacks are then kept, unwatched as they accumulate, even to the point of illness. This hardly seems believable. If it were unregulated, then why is there no obesity epidemic in history even when food is plentiful?
In fact – we already know that this is essentially untrue. We are discovering new hormonal pathways in the regulation of fat growth all the time. The hormone insulin is one of the most important and well-known hormonal regulators of body fat. Leptin and adiponectin are other important pathways. Hormone sensitive lipase may be important. Cortisol may play a role, as well as lipoprotein lipase (LPL) and adipose triglyceride lipase (ATGL). If ‘Body Fat’ is tightly controlled, then it may very well be that reducing ‘Calories In’ will reduce ‘Calories Out’ instead of ‘Body Fat’. So which is it?
What happens when you restrict calories?
The Caloric Reduction as Primary strategy assumes there is a causal relationship between eating too much and obesity. That is, eating too many calories causes obesity, and therefore the solution is to Eat Less calories. This is to distinguish from the other ways of eating less, like eating less sugar, eating less fast food, eating less processed foods etc. Further, this assumes that this is the primary cause of obesity, so that if you ask ‘Why is somebody eating too many calories?’, the answer would be ‘It’s a personal choice’. From a scientific standpoint, this forms a hypothesis that can be scientifically tested, by adjusting how many calories are eaten. What happens when you restrict calories?
The standard ‘scientific’ point of view predicts that eating fewer calories does not affect the ‘Calories Out’ or Basal Metabolic Rate (BMR), and therefore body fat is lost. We’ve all heard this sort of advice. Eat 500 fewer calories per day and lose 1 pound of body fat per week. This assumes BMR does not change.
Let’s look at the gold standard of scientific evidence, the randomized controlled trial. We take some people, give them very little to eat, and watch them lose weight and live happily ever after. Bam. Case closed. Call the Nobel committee. Luckily for us, those studies have already been done.
The first major recent study, the massive Women’s Health Initiative Study was published in 2006. Close to 50,000 women were randomized to either eat their usual diet compared to a low fat, calorie restricted diet, in line with guidelines endorsed and accepted by virtually all medical professionals. The women in the study group ate less (more than 300 fewer calories per day) and exercised more. This group could have expected to lose more than 30 pounds per year in theory. In reality? After 7.5 years they weighed about 0.9 pounds less. After 7.5 years of Eat Less, Move More! What’s worse is that despite a slightly lower weight, the women following the Eat Less, Move More strategy had a larger waist size, suggesting that they carried more of the dangerous fat that accumulates around the midsection.
These underwhelming results would be confirmed in virtually every study done. In 2012, The Diabetes Prevention Program also randomized people to a low calorie, low fat diet. Did the Eat Less, Move More strategy work? Hardly. After a follow up of 10 years, there was virtually no weight difference between the group that ate their usual diet, and the group that deliberately restricted their calories.
In 2013, there was an even more ambitious effort, with the LOOK AHEAD randomized controlled study. Accepting the so-far unproven benefits of the low-calorie diet, the study tested whether an intensive low calorie diet could reduce heart attacks and strokes. Participants would either eat their usual meals or reduce to 1200 – 1800 calories per day, combined with increased exercise.
Compared to eating their usual diet, the intense dieters were able to maintain about a 7 pound weight loss after 10 years on the diet. This sounds pretty good, but it’s not quite true. According to the treatment protocol, if patients did not lose enough weight in the intervention arm, the diet was tightened to as low as 1000 calories per day. If that didn’t work, they could be given weight loss drugs to maintain weight loss. Not quite a fair comparison against diet alone.
But the point was not simply to show that using weight loss drugs could produce weight loss. That would have been pointless. No, the point was to show this weight loss could reduce heart attacks and strokes. This turned out to be an utter failure.
Indeed, the trial was abandoned after 9.6 years of follow up because of medical futility. That is, there was virtually no chance that this intervention would be successful, and there was no point in wasting more time and money on it.
- Low calorie diets combined with increased exercise do NOT result in long term weight loss.
- If you combine with weight loss drugs, you can cause mild weight loss (about 3% of body weight). However, it does not make you healthier in any measurable way.
Not exactly a screaming endorsement for the basic dietary advice given to billions of people all over the world for the last 50 years. No wonder we have an epidemic of obesity and type 2 diabetes. At least we’ve discovered the secret of weight loss doesn’t lie with calorie counting, but it has to do with our hormones.