A combination of factors makes a food fattening. First and foremost, the most fattening foods in our diet are those that we compulsively eat, and not all foods are like this. While many people may have found themselves mindlessly eating a quart of ice cream or a bag of M & M’s, have you ever heard of someone binge eating steak or grilled shrimp?
I love a good porterhouse, but I’d be hard pressed to finish a 16 ounce serving. However a pint of most premium ice creams has about the same amount of calories. Yet somehow polishing that off doesn’t seem very hard.
Besides taste, what causes some foods to be eaten compulsively while other foods can be eaten in moderation with little or no will power? The answer lies in the way foods affect the chemicals in our brains.
Although all foods trigger the reward centers in our brains, some seem to affect it to a much greater extant than others.
Quick digesting carbohydrates, particularly sugar of any type, are the biggest culprits. Researchers at Princeton found that rats fed sugar water have a large dopamine release in their brain. Drugs of abuse, such as cocaine and heroin, cause a release or an increase in dopamine levels in the same area of the brain. This would explain why many people find themselves almost unconsciously eating candies, cookies, and crackers even when they are no longer hungry.
Another characteristic of fattening foods is their ability to raise insulin levels. Insulin is released by our bodies primarily when our blood sugar increases. Certain other foods, such as proteins (particularly those high in branched chain amino acids), artificial sweeteners, and possibly even dairy fat can also increase insulin levels in the body.
I’ll spare you the biochemistry, but insulin makes us fat. Any Doctor who has ever treated a diabetic patient knows this. Treat someone with insulin and they immediately gain weight, even if they are already obese.
In general, foods that increase your blood sugar the most, such as sugars and processed grains, cause the largest release of insulin.
Finally, the most fattening foods are high in calories. This seems obvious but probably accounts for much of the difference between very similar foods. For example, a large glass of OJ has about 250 calories. We would need to eat four oranges to get the same amount of calories! Both oranges and orange juice taste good, they are both high in sugar, and they both cause a rapid increase in blood sugar. In fact, the glycemic index (a measure of how much a standard amount of a certain food increases your blood sugar) of oranges and orange juice are nearly the same. But oranges are inherently low in calories and orange juice in inherently high in calories.