By @FoodLabScience - 8 July, 2017
In 2012 a study based on the National Health and Nutrition Examination Survey determined the BMI, or Body Mass Index, of Americans. Based on their height and weight it was found that only 31% were at a healthy weight or underweight, 33% were overweight and 36% were obese. This means that for every three people in the USA, one is at a healthy weight, one is overweight and the third is obese. The annual medical costs of overweight and obesity are estimated to be $147 billion.
Note that, while BMI shouldn’t be used as a diagnostic tool for individuals, it is a good tool to assess overweight and obesity in populations.
The question that arises is: what causes so many people to become so big? There is no easy answer to this question. However, it boils down to two causes. The first cause is that we eat too much food; the second cause is that we eat the wrong food. Let’s start with eating too much food.
Too much food
The idea that obesity is due to an energy-balance disorder has been the foundation of nutritional science since the 1960s. The World Health Organization says:
‘The fundamental cause of obesity and overweight is an energy imbalance between calories consumed and calories expended.’ Arguing against this reasoning isn’t easy, as it is backed by the first law of thermodynamics. For the human body this means that if energy intake is more than what the body needs, excess energy is stored in energy reserves.
The wrong food
Researchers are now trying to answer the underlying questions. Why do we consume excess energy? And why and how do our fat cells store this energy? Nutritional research has experimented with different diets. They look into the effect of the three macro-nutrients protein, fat and carbohydrate and the caloric content. It was found that as we vary the type of food we eat, the expression of our hormones also changes. The idea that obesity is a hormonal or regulatory disorder, as initially proposed by the German Gustav von Bergmann in the early 1900s, is now starting to gain traction.
But how do hormones influence the storage of fat? This question is, interestingly enough, not answered by looking at fat, but by looking at carbohydrates. The carbohydrates that we eat are broken down to glucose, which is then absorbed in our bloodstream. Our body likes to keep our blood sugar constant, also called homeostasis. It does this with a multitude of feedback mechanisms. If the sugar level in the blood increases after a meal, the hormone insulin is released by the pancreas. Primary tasks of insulin related to fat are:
- It tells muscle, organ and fat cells to use glucose for fuel.
- It tells fat cells to store fat.
Insulin prevents burning fat and increases the likelihood of storing fat, thus keeping insulin levels low will do the opposite. If eating carbohydrates increases our blood sugar level, which in turn increases insulin levels, then limiting carbohydrate intake will increase the likelihood of burning fat.
Whether we eat too much food or the wrong food edges more on the side of the wrong food. While caloric content shouldn’t be ignored completely, it is important to keep insulin levels low by eating less carbohydrates if the desire is to lose fat.