Cortisol is lipolytic, not lipogenic. It mobilizes energy stores, not builds them.
Why is the glycemic index BS?
Cortisol is lipogenic, meaning it directs the body to store body fat. And importantly, as cortisol levels rise, levels of growth hormone and testosterone levels drop, and vice-a-versa.
Glycemic index is if the food is eaten on its own for one, when you mix foods you cannot get a picture of the GI. What matters is calories.
In one of the most recent studies of the glycemic index, researchers from the University of Minnesota tested whether lowering the GI of a diet already low in calories would have any further effect on weight loss.
The researchers compared the effects of three low-calorie diets, each with a different glycemic load, on 29 obese adults. All of the diets high GI, low GI or high fat provided the same number of calories.
For the first 12 weeks, all food was provided to the subjects (the feeding phase). Then, 22 subjects were told to follow the assigned diet for an additional 24 weeks (the free-living phase).
After 12 weeks, all three groups lost weight. However, there was no significant difference in weight loss between the groups. Subjects on the low GI diet lost, on average, 21.8 pounds (9.9 kilograms), while those on the high GI diet lost 20.5 pounds (9.3 kilograms).
"In summary, lowering the glycemic load and glycemic index of weight reduction diets does not provide any added benefit to energy restriction in promoting weight loss in obese subjects," conclude the researchers.
Eating a diet with a low glycemic load can help with weight loss. But, that's largely because many foods with a low glycemic index (with the exception of high-fat foods like nuts and avocados) also have a lower energy density.
Most fruits and vegetables, for example, have a low glycemic load. So, when you eat fewer foods with a high glycemic load (e.g. cookies, cakes, or sweets) and more foods with a low glycemic load (e.g. fruits and vegetables), you end up eating fewer calories. The result is that you lose weight.