Natural selection has favored people who like fatty foods. This is because fatty foods contain lipids, which have the most calories per liter. Therefore, the person who eats the most lipids is the least likely to starve. Evolution has shaped our food preferences. There are 3 important macromolecules:
| Lipids | Lipids stor energy in their C-C bonds. Lipids are water-insolube, and are involved in energy storage, membranes, and hormones. |
|---|---|
| Carbohydrates | Carbohydrates are fuel. The have the empirical structure CH2O. If you encounter a molecule with this ratio, it is a carbohydrate. For example, glucose is C6H12O6. Monosaccharides contain one sugar. Polysaccharides are chains of sugars bound together. Since separating polysaccharides is energetically expensive, they take longer to catabolize. Similarly, monosaccharides provide a quick infusion of energy. |
| Protein | Proteins are for anabolism. Cells and tissues are built mostly from proteins. Proteins are made of sequences of amino acids. |
When caloric intake is reduced as much as 50%, the effects have been shown to be:
The lack of ovulation is typical when diet is restricted (as in anorexic women). Although the positive effects of caloric restriction are negligible in social animals such as humans, the effects in rodents, insects, and microbes are remarkable. The lifespan of a praying mantis is in some cases doubled when the praying mantis is calorically restricted.
There are two well-respected explanations:
|
|
