How Not to Diet

Michael Greger became famous for his first best-seller, but the book that made his name in the United States was about preventing chronic disease, not specifically about weight loss. After its success, thousands of readers started asking about the subject the earlier book only touched on: how to really lose weight and not gain it back afterward.

How Not to Diet was born from that question. It is a hefty book, full of footnotes and references, split into two parts: first, why almost every fad diet fails in the long run; then, a list of what the author calls accelerators, small habits that, added together, help the body lose weight without making you count calories all the time.

The author's starting point is simple: losing weight fast is easy, and almost any drastic restriction works for a few weeks. The hard part, and this is where the whole book lives, is keeping the weight off after one year, two years, ten years, a period most diet studies never even follow.

Greger reviews dozens of popular diets, keto, paleo, intermittent fasting, low carb, the Zone diet, and argues that nearly all of them produce similar weight loss in the short term, because deep down they all cut calories one way or another, even the ones that claim you never have to count calories.

What he tries to prove is that keeping the lost weight off, and not the loss itself, is the real problem, and that overly restrictive diets tend to fail precisely there, because nobody can stand to eat for years the way they ate to lose weight quickly at the start.

What the book does not prove, despite the volume of studies cited, is that a whole-food plant-based diet is superior to any other approach for weight maintenance in a long-term, large-scale randomized clinical trial. That kind of expensive, slow research practically doesn't exist for any diet.

The book's central concept is calorie density, the amount of calories that fit into each gram of food. Leafy greens, for example, have very few calories per gram because they are practically water and fiber, while a handful of nuts or a spoonful of oil packs a lot of calories into very little weight.

The practical idea is to swap part of your plate for low-calorie-density foods, so you eat a volume that fills your stomach and signals fullness to your brain while taking in far fewer calories overall. It's not about eating less, it's about eating differently, prioritizing what weighs more and quiets less hunger.

Greger builds a sort of chart of the most and least dense foods, suggesting you build your plate around vegetables, legumes and fruit, soup and salad, and save the more concentrated items, like oil, sugar, refined flour and fried food, for the smaller occasions of the week.