In late December I started eating low glycemically for diabetes prevention — i.e., for control of blood sugar & fat loss both (not weight loss per se — I’d like to keep & add to my lean muscle weight), as loss of fat around the waist is very important in diabetes prevention & management. But now I would say that eating low GI (which is only one change I’ve made to my lifestyle) is just basic good health sense for anyone & everyone. I simply don’t see how refined overprocessed foods & fast foods which tend to be high GI (not to mention full of unhealthy types of fats) are healthy for anyone. If not sooner, then later: overconsumption of those kinds of foods is the major cause not only of Type 2 diabetes, but also obesity, heart disease, & cancer. Especially when coupled with a sedentary lifestyle.
I don’t regard this as “a diet,” if by “diet” you mean a temporary change in how one eats in order to meet a weight loss or other goal, after which one returns to “eating normally.” It is diet in the sense of “this is my normal daily diet.” Basically, I’ve changed what is a normal diet for me. My normal diet no longer includes fast food, refined foods out of a box, white flour, white rice, white potatoes (they have become very much an exception, because of their high GI), etc. My normal diet now consists of low-GI carbs in moderate portions, along with healthy proteins, fats, & lots & lots of nonstarchy vegetables.
I think that “GI diet” type of book can be helpful to get started on a healthy permanent change in diet like mine, but I think it’s unwise for people to restrict themselves to that. On a list I’m on someone recently wrote to the effect of “just pick a diet & then stick to it”: I disagree. Most diet books are written as “one size fits all”, but one size doesn’t fit all. For example, some people can afford to eat (whole grain) pasta & basmati rice with no ill effects, & find those foods to be a healthy, nutritious part of their low GI eating plans. Others cannot because even in moderate portions those foods send their blood glucose up too high. Some people follow low-carb eating plans; I find that I cannot because if I go to low, I get badly depressed. I eat a moderate-carb diet instead.
But to me, low GI isn’t itself my diet. It’s a good principle of a healthy diet that can be combined with any number of general eating styles — e.g., the “Mediterranean diet,” low carb, moderate carb, high carb, vegetarian, vegan, etc.
The long & short of it is that no matter how good the book you start out with, the only person who can be the expert on what is best for you is you. Read books & websites, participate in discussion & support groups dealing with healthy nutrition & fat loss, & pay attention to your own body’s feedback, your own native intelligence & good sense. Some books will say “thus-n-such food is allowed” but if it makes you more tired after eating it, or gives you acid stomach (something that low GI eating cured for me), or causes your blood sugar to go sky high, or makes you hypoglycemic, then to hell with what the book says: follow what your body says. Never put any book’s or any other person’s expertise ahead of your own intelligent mindfulness about yourself & your body.