Regarding weight loss, the calorie reduction theory has prevailed long enough - it's time to expose this myth.
The theory goes like this. It states that the amount of energy entering the body ("calories in") must equal the amount of energy exiting the body ("calories out"). If this balance is thrown off, the body will either gain energy by storing fat, or lose energy by burning fat. It's so obvious - the amount of fat stored or burned is simply equal to calories in minus calories out. Therefore if a person wants to lose weight, all they have to do is decrease calories in and increase calories out.
Unfortunately, there is a glitch in this simplistic outlook - the calorie reduction theory does not actually work. There are dozens upon dozens of studies demonstrating this but let's illustrate the point with just one of them. The 2006 Women's Health Initiative Trial was the most awesomely designed, kick-ass test of the calorie reduction theory ever done (1). In this trial, the investigators randomized 48,835 women to either an intervention group or a control group for seven years. The intervention group received a series of regimented education sessions throughout the study (42 sessions in total). The control group received none at all.
What happened? For seven years, the intervention group followed the advice they were given - they decreased their mean calorie intake by 20%, increased their physical activity by 14%, and lowered the fat percentage of their daily calorie intake by almost 10%. The calorie reduction theory predicted that these women ought to have lost nearly 15 kg by the end of the study. In reality, the mean weight loss after seven years was not even 1 kg.
That's quite a shortfall. By eating less, moving more, and lowering the fat, it was predicted that these women would lose nearly 15 kg over seven years, yet they did not even lose 1 kg! This is one of many studies showing that the calorie reduction theory is seriously lacking. Clearly, it's not "all about the calories." Yet the medical profession continues to preach this sermon.
The calorie reduction theory contains many faulty assumptions - let's be nice and just focus on two of them.
Calorie Reduction Theory - First Faulty Assumption
The first faulty assumption about the calorie reduction theory is that "calories in" is independent of "calories out." The reality is that when one of these two variables is altered, the other one changes accordingly.
If food intake ("calories in") decreases then the body's basal metabolic rate ("calories out") also decreases and vice versa, a physiological fact that has been known for 100 years (2). Even the infamous Dr Ancel Keys demonstrated this in his mid-1940s Minnesota Starvation Experiment when he subjected 36 healthy men to a 50% reduction in food intake ("calories in") and noted that their basal metabolic rate ("calories out") correspondingly fell by 40% (3). The reason for this is that the body tries to maintain a sustainable energy balance; if "calories in" decrease, "calories out" must also decrease or the body will eventually run out of energy and perish, and the body does not want to perish (4). So eating less simply results in a compensatory lower basal metabolic rate, and thus eating less does not lead to long-term weight loss.
Try eating 10% less calories per day ("calories in") without adjusting your activity levels ("calories out") and see how much weight you lose over the course of several months. The answer is none. Your body will simply lower its basal metabolic rate by 10%.
Likewise, if the body's physical activity ("calories out") increases then its food intake ("calories in") also increases and vice versa; it is commonly known that physical activity works up an appetite. The ultimate method for increasing "calories out" is exercise, and yet it is well documented that for every extra hour that a person exercises, the more calories they eat to match the increase in energy expenditure from that exercise (4). Picking one example to illustrate the point, a prospective study involving 538 students showed that for every extra hour of exercise done, the students ate an extra 292 calories (5). Again, the body wants to maintain a sustainable energy balance; if "calories out" increase, "calories in" must also increase or the body will run eventually out of energy and perish. So exercising more results in a compensatory higher food intake, and thus exercise does not lead to long-term weight loss.
Try running for one hour three times a week to increase your "calories out" without adjusting your "calories in" per day. See how long you last. The answer is several weeks or months at most, depending on how much weight you carry. Your body will tire of the facade and force you to increase your caloric intake before it enters a serious state of wasting.
Therefore itis extremely difficult to achieve long-term weight loss by decreasing "calories in" or increasing "calories out". If "calories in" decreases through eating less, "calories out" compensatorily decreases. If "calories out" increases through exercising more, "calories in" compensatorily increases. It is largely for this reason that any attempt to achieve long-term weight loss by eating less or exercising more is associated with a 99% failure rate in the literature (4).
Calorie Reduction Theory - Second Faulty Assumption
The second faulty assumption is that a calorie is a calorie, implying that all calories are equal. The reality is that calories from different foods provoke very different physiological responses within the body.
When a person consumes carbohydrates, especially processed carbohydrates in which the fiber and fat are artificially removed (think flour and sugar), the pancreas releases the hormone insulin to deal with the rise in blood glucose. Insulin has many roles, and one of them is to distribute carbohydrate-derived "calories in" into fat storage; ask anyone with diabetes who is taking insulin injections and they will flatly inform you that insulin makes you fat. There are dozens of studies documenting this but we'll just mention one of them to get the point across. In the landmark 1993 Diabetes Control and Complications Trial, a high dose of insulin was compared to a standard dose of insulin in 1,246 type 1 diabetes patients over six years - by the end of the study, participants in the high-dose group gained 4.5 kg more than those in the standard dose group (6). It is a verifiable fact that more insulin equals more fat storage equals more weight gain. Since processed carbohydrates stimulate the pancreas to release insulin more than any other type of food, more processed carbohydrates equals more fat storage equals more weight gain.
Try eating 65% processed carbohydrates, 30% proteins, 5% fats for the next couple of months and see if you gain weight. The answer is yes, you will. The presence of insulin will force your body into fat-storage mode; it has no choice.
In contrast, a different physiological response occurs in response to the consumption of pure fats (think olive oil, coconut oil, and butter). Fats do not produce a spike in blood glucose levels and therefore have a very weak insulin-stimulating effect. If insulin levels are low, fat-derived "calories in" do not get rushed into fat storage and are distributed throughout the body to one of several possible destinies including heat production, protein synthesis, and cognition (the brain consumes 25% of the body's basal metabolic energy) (4). This means less fat storage and less weight gain, or even weight loss. Picking one example to illustrate the point, a well-designed 2008 study randomized 322 moderately obese patients to either a restricted low fat diet, restricted Mediterranean diet, or unrestricted high fat diet for two years - while each of the three groups managed to decrease "calories in" and increase "calories out" for two years, there was no significant difference in "calories in" and "calories out" between each of the three groups, and yet mean weight loss at the finish line was 2.9 kg in the low fat diet group, 4.4 kg in the Mediterranean group, and 4.7 kg in the high fat diet group (7).
Try eating 65% fats, 30% proteins, 5% carbohydrates for the next couple of months and see if you lose weight. The answer is yes, you will. The blunted insulin levels will free up your body's metabolism to distribute most of that energy into heat production, protein synthesis, cognition, and elsewhere rather than just shunting most of it into fat storage.
Therefore when it comes to weight loss a calorie is NOT a calorie. Many carbohydrate-derived calories crank up insulin and are rapidly shunted into fat storage. Fat-derived calories, since they do not spike blood glucose or insulin, are distributed throughout the body to a variety of destinies. Protein-derived calories lie in between. This may be the primary reason that eating processed carbohydrates makes you fat, while eating fats does not make you fat. According to the literature, the traditional low-fat dietary food pyramid (with bread, cereal, rice, and pasta at the base of the pyramid) actually encourages obesity.
The Way Forward
Despite its astonishing failure as evidenced by the epic rise in the metabolic syndrome (abdominal obesity, high blood glucose, high blood pressure, and distorted cholesterol levels thus setting the stage for heart attacks and strokes), the calorie reduction sermon continues to be pedalled by mainstream medicine to this day. If an overweight individual visits a medical professional for advice, they will invariably be told to eat less, exercise more, and stick to a low-fat diet despite decades of evidence showing that none of these strategies work in the long run.
What advice should medical professionals be giving instead? Brace for impact. Instead of eating less and exercising more, the advice ought to be "eat until you are satisfied" and "exercise for muscle health, not weight loss." Instead of sticking to a low-fat diet, the advice ought to be "avoid processed carbohydrates, eat mostly natural fats." Although I am simplifying things here, I strongly suspect that if medical professionals did nothing else but offer this advice to their patients, the metabolic syndrome's stranglehold on human health would be far less potent than it is today.
When a patient fails to lose weight, or loses it for a few months but then "inexplicably" gains it back, a number of medical professionals do the unforgivable and choose to blame the patient rather than question their own flawed advice. There is lots of head shaking followed by a bit of self-affirmation: "Well it's not my fault - it's your fault for not sticking to my advice!" Yet recall the Women's Health Initiative Trial - the 48,835 women in that long-term study dutifully followed the advice they received for seven years. By the end of those seven years, they had decreased their mean calorie intake by 20%, increased their physical activity by 14%, and lowered the fat percentage of their daily calorie intake by almost 10%. These women followed the advice they were given. The result of all of their efforts? Not even 1 kg in weight loss.
The interaction between a medical professional and a patient is like a mirror. At the end of the consultation, the medical professional offers some recommendations to the patient. Concurrently, the medical professional ought to be questioning and observing the results of those recommendations.
Unfortunately, I do not think that some medical professionals want mirrors.
They want windows. Solace.
References (1) Howard BV, Manson JE, Stefanick ML, Beresford SA, Frank G, Jones B, Rodabough RJ, Snetselaar L, Thomson C, Tinker L, Vitolins M, Prentice R. 2006. Low-fat dietary pattern and weight change over 7 years: the Women's Health Initiative Dietary Modification Trial. JAMA 295(1), 39-49. (2) Benedict FG. 1919. Human vitality and efficiency under prolonged restricted diet. Washington Carnegie Institution of Washington. (3) Keys A, Brozek J, Henschel A, Mickelsen O, Taylor HL. 1950. The Biology of Human Starvation. University of Minnesota Press. (4) Fung J. 2016. The Obesity Code: unlocking the secrets of weight loss. Scribe. (5) Sonneville KR, Gortmaker SL. 2008. Total energy intake, adolescent discretionary behaviours and the energy gap. International Journal of Obesity 32, S19-S27. (6) The Diabetes Control and Complications Trial Research Group. 2001. Influence of Intensive Diabetes Treatment on Body Weight and Composition of Adults with Type 1 Diabetes in teh Diabetes Control and Complications Trial. Diabetes Care 24(1), 1711-1721. (7) The DIRECT Group. 2008. Weight Loss with a Low-Carbohydrate, Mediterranean, or Low-Fat Diet. NEJM 359, 229-241.