No Fat? No Carb? And What About Protein?
Macronutrients come in three types - fat, carbohydrates, and protein. The gross calories of each are 9, 4, and 4. However, some calories are needed to digest what is eaten, so the actual impact of those calories is less. For example, the cost of storing fat is 1.7 calories per gram, so an effective net carbohydrate availability would be 7.6 calories per gram (metabolic energy kcal/g minus cost of storage kcal/g). After burning the energy necessary to store carbohydrates, the net calories are.6. Protein uses 6 calories to store. Weight change to the body in grams per calories also varies by macronutrient. Carbohydrates change in grams per kcal is.3, and fat is.21 to.12. The change in weight from protein calories is unknown, but the negative net availability would imply a negative gain.
Weight Loss and Weight Gain - Genetics
How individuals process macronutrients varies according to genetics and personal history. Some people are genetically predisposed to gain weight, while others are genetically more round. Studies of twins separated at birth and raised in varying environments suggest that genetics explain a high degree of weight variance in people. The twins were raised in environments that promote varying degrees of healthful diets with adopted parents who are either fat or thin, yet still both twins mirror each other's physique. Both twins were thin even though one twin's adopted parents were obese. And other twins were heavy even if one twin's adopted parents were thin.
Weight Loss and Weight Gain - Personal History
History does explain non genetic weight issues. Since the discovery of the first adenovirus likely to cause obesity, studies have discovered two more adenoviruses linked to obesity. Work at the University of Wisconsin, Madison, found that a much higher percentage of fat people (more than 20% overweight and struggling to get rid of it) have been exposed to different adenoviruses than skinny people. There are 50 different adenoviruses, some causing the common cold. Since the first discovery that more fat people have been exposed than skinny people to one of those adenoviruses, two more adenoviruses have been added to the list. Studies also show that mice and chicken exposed to the same viruses get fat! The significant results of these studies indicate that some of these adenoviruses cause obesity.
Weight Loss and Weight Gain - Cellular Changes
But the story may not end with genetics and viruses. In addition to processing macronutrients according to our unique genetics and history, the fat cells of obese people mutate in a significant way, becoming a force that works hard to maintain the weight problem. This is where set point and the normal weight maintenance mechanism of the body comes in to play. In people whose weight maintenance mechanism works, the brain tells the body to eat less and move more when weight is above the natural set point. When the personal history, or a less common genetic makeup, causes the brain to fail in its weight maintenance, the brain sends signals opposite of what is appropriate. The brain tells the body to feel tired and drained, spend less energy, and eat more.
Studies on Mice Reveal Interesting Facts about Weight
Several studies have used mice specially bred to mimic the obesity patterns of humans. Mice are used because their metabolisms are close to metabolism of people. The Zucker rat exhibits signs that mirror American obesity progression. They eat more, make more insulin but still have normal blood sugar, have high triglycerides, develop enlarged fat cells and a higher number of fat cells, and experience a high incidence of type II diabetes and kidney complications. In the Zucker rats, obesity is likely caused by an important enzyme to the development of fat tissue called Fatty Acid Synthetase (or FAS), which is 25 times higher than in normal rats.. [When Fatty Acid Synthetase is inhibited, the mice rapidly lose stored fat (Schleinitz, et al., 2010).]
The larger fat cells behave differently than the fat cells of normal rats. When these fat cells are removed from the rat, they continue to behave the same way. This means that the cells themselves have changed. (International Journal of Obesity 1992,16: 213-8) Journal of Lipid Research, 1992 Part of the problem might be linked to higher than normal protein needs. These altered fat cells break down protein easier than fat, so the Zucker mice tend to have low muscle mass. In order to have sufficient muscle mass, the rats overeat in an attempt to get extra protein for their muscles. The extra carbs and fat they get trying to get enough protein turns to fat. (Obesity and Leanness - Basic Aspects) (Metabolism 1991;40;3:280- 5)
Obesity, Weight Gain, and High Protein Needs
Finally, protein is one of the few nutrients, and the only macronutrient, that the body cannot store. If humans do not get their daily requirements of protein, the body steals it from the muscles, much the same way that the body will steal calcium from bones when intake is insufficient. The muscles are important in regulating the body's metabolism. Muscle weakness and muscle loss can result in decreased muscle sensitivity to insulin, which results in higher insulin levels. The higher insulin levels interfere with the body's weight maintenance mechanism further and/or cause it to fail. The brain sends the wrong signals, telling people to eat more, move less, and burn fewer calories. People feel drained, not well, and unhappy.