Iíd like to start a discussion on theories of weight control (dieting, but also difficulties in maintaining or gaining weight). In particular, calories in/calories out (the move more/eat less camp) versus hormonal control. Both are involved but which one is more of an issue in long-term success?
My personal bias is that a nutritional theory should be consistent with the known biochemistry. Understanding the actual pathway is more important to me than how a study is interpreted. If the study results appear to contradict the biochemistry then I want to know why. Some cult status nutrition writers gloss over the ďscienceĒ and throw insults at those who donít agree with them; I kind of enjoy reading those books but theyíre not convincing to me. My other disclosure is that Iím an entrenched omnivore looking for nutrient density across each macronutrient, and to me it means both animal and plant material.
My comments on this post reflect Jason Fung. One of the more important books Iíve read is The Obesity Code. (This puts me in the hormonal control camp.) Fung also has an awesome blog. Two recent beauties:
According to Fung, the First Laws of Thermodynamics (the one that supports calories in/calories out) doesnít let you predict how much weight youíll lose because whether we burn calories or whether they go towards fat storage is tightly controlled by hormones, primarily insulin. Insulin is the fat storage hormone and it also blocks release of fat from fat tissue. His theory is that traditional diets fail because they donít account for insulin. Insulin does not respond to calories equally; it rises highest in response to rising blood sugar levels but that isnít the only trigger. In The Obesity Code, Fung explains that even the physical act of eating, of food passing from the mouth to the stomach, stimulates insulin. In long-term caloric restriction your body must reduce basal metabolism to fit the calories or energy available. Exercising burns hardly any calories compared to your overall energy needs but it does help with insulin resistance and some other health issues. Exercise also tends to ďwork up an appetiteĒ.
Fung is a firm believer that diets work when you get right both what you eat and also when. For Fung, the when part is giving your body a chance to work through stores of blood sugar and glycogen while damping insulin triggers so you have a chance to draw on fat reserves for the bodyís energy needs. Intermittent fasting isnít required but it can be an efficient way to achieve this. In caloric restriction, youíre hungry because your energy needs arenít being met; in fasting, your energy needs are met. Thatís after a period of adjustment, which personally, Iím not in a hurry to find out how long that period of adjustment would be for me. ;^)
Fung also discusses weight set point as one of the reasons why he feels calories in/calories out doesnít work. Your body strives to maintain or re-establish the prior set point, the weight we trend towards whether weíre trying to gain weight or lose it. Severe caloric restriction (not the same as fasting) can result in a lower basal metabolism without a change in set point. So after losing all that weight you may be stuck with continuing to each much less (even adjusting for less body mass) or else risk gaining it all back because itís very difficult to resist continuing hunger after a long period of deprivation.