During our reading of the South Beach Diet for our review, we came across a statement by Dr. Agatson that “the major problem that I have with the Atkins diet is the liberal intake of saturated fats.” (p. 23). In Fact, the South Beach Diet goes out of its way to stress that it recommends the use of the right fats in its plan. The common perception of fat is frequently that of something to avoid, and that perception spawned many diets that were based upon the idea of limiting consumed fat. But, like most ideas to lose weight that concentrate on just one aspect of the problem, classifying all fats to be universally bad is just too simple of a solution. In fact, recent research tends to suggest that all fat is not the same, and that some kinds of fat may, in fact, be very beneficial to overall health. In this article, we explore some of the science of saturated and unsaturated fats in diets, how consumed fat may affect losing weight. In this first part, we offer a background of how the brain controls appetite based on information from hormones and fatty acids in the bloodstream.
Background on Weight Gain and Loss
Michael Schwartz and Daniel Porte Jr., in their background article on Diabetes, Obesity and the Brain (Science, Vol .307, Jan. 2005), write that there is evidence that indicates that the brain processes information from hormones such as insulin and leptin, as well as processes signals from food – like the amount of circulating fatty acids in the blood stream. This information helps the brain regulate food intake and metabolism (energy consumption).
Broadly paraphrasing that article, our bodies are powered by two sources of energy. One source of energy is the food that we consume, while the other is our stored body fat. Over many years, our bodies evolved a system that is designed to avoid the state of starvation. That system naturally stores energy in the times of plenty, and burns off the stores in the times when there is insufficient food. However, this system requires some regulation – a mechanism that would control how much food to store during the “good times”, and when to start using the body fat that was stored away in the “lean times.” Under normal conditions, this mechanism works as intended, controlled by our brain. Our brain, which is an incredibly complex electro-chemical computer, receives various inputs, processes information, and sends out instructions to continuously adjust to the situation at hand.
Over a long period of time, certain parts of the brain evolved to react to the current situation regarding our food – and to ensure that the body’s cells and tissues do no starve. There are two key hormones (chemical signals) that are involved in informing the brain (1) how much food is available, and (2) how much body fat (stored energy) the body has. Those two hormones are insulin (produced by the pancreas) and leptin (most of which is produced by the body’s fat cells). Furthermore, the brain seems to be able to detect fatty acids circulating in the bloodstream and incorporate that signal in the way it processes information from leptin and insulin. It is theorized that these signals are relatively easy to understand – generally, more fat equals more leptin produced, which to the brain means lots of energy stored away. On the other part of the equation, more food eaten generally equates to more sugar in blood, which requires more insulin. To the brain, more insulin means absence of conditions of starvation. The increase of insulin serves as a signal to the body cells to start using glucose as an energy source, and stops it from using fat as an energy source (Wikipedia). When there is a low amount of insulin present, fat is broken down, and used an energy source. Excess food generally results in energy (food) being stored away as fat “for later use.” This is also why most diets also attempt to limit the number of calories (energy) that a person consumes – this allows brain to start thinking that food is scarce, so it should switch to burning body fat as an energy source. The result, in theory, is weight loss.
However, like with any well-designed systems, there are weak points. If there is interference to the way that the brain receives or reacts to these inputs, it can’t issue correct commands to stop eating or moderate energy usage. This condition of interference is frequently called leptin or insulin resistance, which generally means that the cells of the body do not react normally to the increasing amounts of insulin in the blood stream. Insulin resistance is considered by many to be one of the precursors of Type 2 Diabetes (Science Magazine, Vol. 307, Jan. 2005 p.378), and it is believed to be one of the mechanisms of weight gain. It is important to note that this cannot be self-diagnosed – only your physician can properly advise you if you suspect that you developed this condition.
In part 2 of this article, we explore the impact of palmitic acid on appetite control, and the research that suggests that palmitic acid could have a role in the development of insulin resistance (causing the gain of weight and fat).
Go on to part 2 of the Low Carb Diets, Weight Loss and Fat Article.
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