For the vast majority of human history, survival has been a desperate effort with a mixture of luck and lot of vigor. Energy sources have been scarce, and consequently, traits that optimized energy storage and conservation have gained prominence. In response to this history, we have utilized technology to create an environment where energy sources are ubiquitous, cheap, and tasty. Additionally, we have developed social paradigms that frequently revolve around food (tell someone that you are fasting and watch for their response). This is an evolutionarily developed cultural response. Our bodies are programmed to seek, store, and conserve energy and everything from our physiology and anatomy to our metabolism and brain are constantly serving that objective.
If you look at energy partition in the body, the vast majority of energy in our body is stored as fat in the form of triglycerides. However, there are strict feedback mechanisms that make it difficult to liberate these reserves. For example, after eating a mixed (carbohydrate, fat, protein) sourced meal, our bodies shift into energy storage mode for up to 4 hours after a meal. Then why are we told to eat small meals throughout the day? Since the majority of human evolution took place in a period when food sources were inconsistent, I would conjecture that this advice is the result of our evolutionary history impacting our culture. We are programmed to consume food whenever it is available. However, the problem arises (as in our modern environment) when it is always available.
Weight gain most often results from small excesses in dietary intake over a period of time. For example, as little as 25 excess calories (1 apricot per day) in a day can result in a weight gain of 1 kg per year. Food restriction or macronutrient (low carbohydrate or low fat) limiting diets are touted as the main strategy for weight loss, however, these are unsuccessful for the majority of the population because of the overwhelming metabolic and behavioral barriers. For example, in support of low carbohydrate diets, it is a prevalent myth that excess carbohydrates are converted into fat. However, the modern diet results in mild to moderate overfeeding and in such a scenario the glycogen reserves are a sufficient sink for excess carbohydrates and consequently, excess carbohydrates are not converted into fat. In fact, this biochemical pathway is relatively costly and only occurs on a limited basis in severely excessive carbohydrate intake. Therefore, even if you are on a low carbohydrate diet but in a calorie surplus from fat sources, your weight loss will be mitigated and your body fat percentage will not change significantly. The overwhelming source of triglycerides in your adipocytes (fat cells) is dietary fat. Any dietary fat that is not utilized is stored as triglycerides in fat cells. Literally, it is the fat that you eat that makes you fat. On the other hand, low fat diets fail partly because carbohydrates serve as the primary regulators of fat breakdown via insulin. Carbohydrates put the brakes on fat breakdown. Thus, the more carbohydrates you eat, the more insulin is secreted in the blood stream and less fat is oxidized as a food source. Furthermore, low fat diets often leave you unsatisfied and persistently hungry and we inevitably succumb to the temptations of food.
It has repetitively been shown that diets that recommend single macronutrient depletion might be effective in the short term but are not sustainable. After an initial period of weight loss, the yields are often given up as people usually cannot sustain the stringent restrictions. It is difficult to completely sacrifice food staples such as bread, butter, and rice that have been present in our diets for 10,000 plus years. In the short term, these diets may produce weight loss, but their effects are generally transient.
I recently saw a novel proposal of a food triangle (shown below) based primarily on energy density. It works on the premise that proteins are not limiting nutrients in any whole food diet that meets daily energy requirements. Therefore, they propose that food choices should not be driven by fuel sources (ie carbohydrates or fats) but by micronutrient and fiber rich food sources such as cruciferous vegetables, stems, bulbs, mushrooms, and leafy green vegetables. According to this paradigm, these foods should be the nutritional foundation of daily meals and can eaten in nearly unlimited quantities. This organization enables individuals to focus on their micronutrient requirements without driving over-consumption.
Traits that seek, conserve, and optimally store energy in the form of fat are naturally selected for because we largely evolved in an environment where food sources not readily available year round. Any excess calories is stored in our bodies as fat or carbohydrates. Dietary fat is stored as triglycerides in your adipocytes, the carbohydrates and protein that we eat inhibit fatty acid oxidation and is stored as glycogen in our liver and muscle cells. We are battling against hundreds and thousands of years of evolution when we attempt to lose weight. Then if we do manage to lose that weight and want to maintain that weight loss, that battle changes to one against our cultural norms. It is no surprise and completely predictable that for the vast majority of us, this is a losing proposition. However, a food triangle based on energy density takes the focus of fuel sources and puts it on micronutrients. This strategy not only optimizes our micronutrient requirements but also sets in motion a set of epigenetic changes that decreases the oxidative and inflammatory load on our cells and DNA (more about this in the next blog). Maybe Michael Pollan was on to something when he said: “Eat food, not too much, mostly plants.”