How Not to Diet

by Michael Greger

In the Dietary Inflammatory Index, the single most anti-inflammatory food is the spice turmeric, followed by ginger and garlic, and the most anti-inflammatory beverage is green or black tea.

In the landmark study published in 2015 entitled “Which Foods May Be Addictive?” that I mentioned in the Low Glycemic Load section, dozens of foods were ranked based on reports of problematic, addictive-type behaviors from hundreds of individuals. The two most troublesome were high-fat, high-sugar combos: chocolate and ice cream. Most at the top of the list were high in fat, but every single one of the top fifteen was a processed food. In contrast, all the foods least likely to be associated with addictive behaviors were unprocessed. The bottom ten least-addictive foods were strawberries, apples, corn, salmon, bananas, carrots, brown rice, cucumbers, broccoli, and beans.1639

A comparison of dietary quality of popular weight-loss plans scored Ornish’s low-fat, plant-based diet the highest and Atkins’s low-carb, more ketogenic diet the lowest.2447 In general, using a variety of nutritional quality indexes, researchers found that the more plant-based people eat, the healthier their diet scores.2448 Ironically, even though plant-based eaters are restricting entire categories of foods, they end up getting more nutrition. A paper entitled “A Vegetarian Dietary Pattern as a Nutrient-Dense Approach to Weight Management” found that those eating more plant-based were getting higher intakes of nearly every nutrient: more fiber, more vitamin A, more vitamin C, more vitamin E, more of the B vitamins thiamine, riboflavin, and folate, and more of the minerals calcium, magnesium, and iron.2449 This came as no surprise. The Journal of the American Dietetic Association editor in chief responded, “What could be more nutrient dense than a vegetarian diet?”2450

Even those who are young and healthy with no health issues appear to have little problem sticking to a plant-based diet. There was a crossover study in which women were instructed to eat plant-based foods for a few months to see how it would affect their menstrual cycles. But then they were to switch back to their baseline diets to note the contrast, a so-called A-B-A study design where you reverse the experimental variable. The problem is that some participants felt so good eating healthfully—they were losing weight without any calorie counting or portion control, they had more energy, their periods got better, and they experienced better digestion and better sleep—that some refused to go back to their regular diets, which kind of messes up the study.2462 Because they didn’t comply with the protocol and go back to their baseline diets, their data had to be thrown out. So, ironically, the plant-based diet worked a little too well.

The strategy is improving the quality of the food rather than restricting the quantity of the food.

Are the lower disease rates associated with plant-based eating due directly to the diet itself or indirectly to the ease of weight loss and maintenance? To find control groups of individuals eating typical diets who were as slim as a group of whole-food vegans, studies have had to recruit long-distance endurance athletes running an average of forty-eight miles per week for twenty-one years. Apparently, people who run the equivalent of almost two marathons a week for two decades can be as slim as a vegan no matter what they eat! What’s more, the purely plant-based eaters in the studies were sedentary, exercising for less than an hour a week.2478 So run two thousand miles a year, and your weight may rival that of some vegan couch potatoes? What’s their secret? The simplest explanation is that those eating more plant-based may just be eating fewer calories—as many as 464 fewer calories a day, in fact.2479 That would certainly do it. That’s nearly the 500-a-day caloric restriction recommended in the federal dietary guidelines for weight loss.2480 But this calorie reduction was achieved without significantly changing the amount of food eaten. Some studies show that those eating purely plant-based diets are actually eating nearly a half pound more food a day compared to nonvegetarians.2481 That’s the beauty of foods with low calorie density: more food, less weight.

A study in Israel, for example, found that vegetarians weighed about twenty pounds less than nonvegetarians, yet they appeared to be eating about four hundred more calories every day.2486 As we saw in the High in Fiber-Rich Foods section, it’s not what you eat but what you absorb, and the Israeli vegetarians were eating extraordinarily healthy diets, averaging nearly seventy grams of fiber a day. This could help explain why those eating more whole plant foods seem to lose more weight even at the same estimated caloric intake.2487 Interestingly, a similar paradox arose in rural China at even half the fiber intake.2488 Before the Westernization of their diets, the rural Chinese got about 90 percent of their protein from plants. Even the least active “office workers” ate 30 percent more calories than Americans, yet were 25 percent leaner.2489 Of course, they may have been biking to the office or something, but the calories still didn’t seem to add up. It turns out that those eating more plant-based may effectively be burning more calories in their sleep.

Fiber is a smuggler.

Dietary fiber alone has certain benefits, but its primary role may be to encapsulate nutrients for special delivery to our gut microbiomes. If there’s one recurring theme in this book, it’s wall off your calories. Make sure as many of your calories as possible—your protein, your carbs, your fat—are encased in cell walls. Cell walls are made out of fiber, which acts as an indigestible physical barrier, so when you eat structurally intact plant foods, many of the calories remain trapped. Chew all you want—you’re still going to end up with calories completely surrounded by fiber, which then blunts the glycemic response, activates the ileal brake, and delivers sustenance to your friendly flora. That’s what nature intended to happen.

If you could only make one dietary change, getting rid of sugary beverages would be a good choice and one that is consistent with my advice to wall off your calories. That means eliminating soda sweetened with sugar or corn syrup, as well as other sugary drinks, both carbonated and uncarbonated, such as sports and energy drinks.