Insulin sensitivity is probably the most important aspect of physique enhancement in normal, healthy inidividuals. This is because it is the most often misunderstood.
Insulin is the most anabolic of the body’s hormones, but it is good at promoting both muscle and fat gain. When the human body’s muscles are depleted of glycogen (post workout) insulin sensitivity is almost always high. Some people, however, have generally high insulin sensitivity. These people, the “lucky” ones, are the individuals where insulin is likely to feed their muscles carbohydrates during normal meals. The “unlucky” people, who have low insulin sensitivity, once their muscle’s glycogen level has been replenished, insulin will tend to feed their fat cells. This means that the same number of calories of carbohydrates, will make these individuals fatter than the same kcal of protein or fat (because protein has only a small effect on insulin secretion, and fat has none).
Usually, individuals complaining of a “slow metabolism”, actually have poor insulin sensitivity. This is why, although low carb diets are not right for everyone, they are right for the vast majority of people who need to lose weight. Poor insulin sensitivity is much more prevalent than a “slow metabolism.”
Lack of knowledge regarding diet, and a tend to focus on nutrition facts, rather than actually learning about food… Tends to lead these overweight individuals towards diets where they still eat carbs, but barely eat anything. Few of them realize that if they capped carbohydrates off at 150 grams per day, that they would have never gained weight, even with all you can eat red meat. Frequently the sole focus is the calories, and these individuals, frequently women, will say, “Hey, I’m eating 1,700 kcal a day, and I’m gaining weight, therefore I am going on a diet, and eating 1,250kcal a day.” Their soul focus is the calorie. Little do they realize, they are fat because they are eating cereal, bread, sweetened beverages (this is the absolute worst thing you can ingest), dairy, and all the things that tend to cause high blood sugar spikes.
You know how calories are calculated? Things are lit on fire, and the amount of heat they release is measured, using a calorometer (I think its called?). It is a physical measure of the amount of chemical energy in a food, and a massive oversimplification of the human body.