The science and art of weight loss is misunderstood by a great many who claim expert credentials and deliberately obfuscated by a small number more. We are told that weight gain results from a simple disruption to the energy balance equation, such that energy intake becomes greater than energy expenditure. This ultimately results in an accumulation of energy that is retained in the individual in the form of body fat. Reversal of this process, we are told is simply a case of increasing energy expenditure or decreasing energy intake to produce a negative energy balance. Interestingly, the cause of weight gain is often attributed to either the greed or laziness by the individual and recommendation is forced calorie restriction or a regimen of vigorous exercise. Select almost any medical text book or dietician’s reference from the shelf and this assumption will be present, often with referral of the reader to the first law of thermodynamics as way of evidence.
The first law of thermodynamics is well known and in simplified form states that energy can be converted from one form to another but cannot be created or destroyed. In nutrition, humans consume energy in the form of food that contains chemical energy in the bonds of the molecules. Digestion and metabolism break down the molecular structures of the food to simpler chemicals and as this process occurs the energy is harvested to do useful work. Traditional thinking supposes that supply of too much energy in the form of food oversupplies the body with energy which is in excess of the work it needs to perform. As a result the excess energy is used to create fat molecules, which are subsequently stored in adipose tissue as body fat. We are told the only way to remove this fat is to either reduce the amount of food ingested or increase exercise, so that the body draws on its supply of fat to fuel its work.
The main problem with the assumption that overeating or lack of exercise causes weight gain is that is ascribes the cause and effect without scientific due process. The fact that individuals with a higher body weight eat more food is self evident and can be observed scientifically with nothing more that a set of scales and a food energy table. However, this observation does not allow one to ascribe the cause and effects between the two parameters. While we can state that the energy intake of the overweight individual has been in excess of the amount of energy needed to perform work, we cannot necessarily state that it is the overeating that has caused this weight gain. It would, for example, be equally correct to suggest that the weight gain had caused the overeating. For while it is true that the first law of dynamics must be maintained in human nutrition, we do not need to ascribe cause and effect to maintain the law.
Before considering further the possible causes of unhealthy weight gain it is necessary to pay some consideration to the mechanisms by which bodyweight is maintained. Under normal conditions, humans can regulate their bodyweight to a fine degree despite large fluctuations in exercise and food intakes. Under normal conditions, the body weight of a healthy person will remain stable for long periods of time, perhaps a whole life time. This is possible because mammals possess an intricate system of feedback loops that inform the food centres of the brain about parameters such as blood sugar, energy reserves, recent food intakes, stomach fullness, muscle glycogen reserves and many other important energy related parameters. In health individuals as food intake is increased, both energy expenditure and satiety are increased in a compensatory fashion. Likewise if energy intake falls, energy consumption is curtailed and hunger is stimulated to ensure adequate energy for normal metabolic regulation.
The healthy individual has therefore every expectation that energy balance will be maintained through this complex system of regulatory feedback. High quality food from a mixed diet will contain all the necessary nutrients and co-factors needed for the correct functioning of this system. Of particular importance is the supply of glucose and the release of insulin. Glucose provides good energy for skeletal muscle and a limited amount can be stored within the muscle tissue as glycogen. To pass into the muscle cells glucose molecules require the hormone insulin, which is released during digestion of carbohydrates to glucose. Insulin acts as a key to open the cellular passage of glucose into the muscle cells, and full glycogen stores are strong signals to the brain that curtails further food intake. In this way glycogen provides a break on subsequent unnecessary food consumption and also provides a ready supply of energy to the muscle that allows vigorous exercise.
However, because this process is reliant on the hormone insulin, a dysfunction in the insulin system can cause a disconnection between perceived and actual energy intake. Damage to the insulin receptor for example, reduces the ability of the insulin to shuttle glucose into the muscle cells which as a result become depleted of glycogen. Because glycogen is the fuel required by muscle tissue for vigorous exercise, the first symptom of this problem is an apathy and substantial reduction in physical performance. The second problem with a defective insulin receptor is that the glucose that would have been stored in the muscle tissue, is instead diverted to the fat cells, where it is converted to body fat and stored. The third major problem with this dysfunctional system is that energy reserves have not been adequately restored as the muscle tissue does not have enough glucose for production of energy, and so appetite for carbohydrate foods is stimulated, exacerbating the problem.
We see therefore that metabolic dysfunction can cause a misallocation of food energy into the wrong storage location and this in turn can stimulate increased food intake and prevent exercise. This situation maintains the first law of thermodynamics because no energy has been created or destroyed, and yet reverses the cause and effect attributed by the traditional viewpoint of weight gain. The main difference between the two hypotheses is that the traditional allopathic medical viewpoint blames the individual for greed and laziness, while the second blames a metabolic dysfunction that causes a homeostatic imbalance. If we take this a step further, we can ascribe blame in the second case to whatever caused the metabolic dysfunction. This is likely the food and soft drink industry, that has systematically engineered the Western food supply to contain nutrient deficient foods that are high fructose and sucrose, both of which are known to be a direct cause of insulin receptor dysfunction.
RdB