How Not to Diet

by Michael Greger

Within twenty-four hours of switching between the two diets, there was a substantial shift. So, to answer the question: basically as soon as food hits our colons.

On the plant-based diet, the subjects’ guts yielded more protective short-chain fatty acids, fewer carcinogens, and less of the rotten-egg gas hydrogen sulfide. Hydrogen sulfide is made by pathogens such as Bilophila wadsworthia, which increased on the animal-based diet.

The benefits of plant-based eating need not be all or nothing, though. Those highly adherent to a Mediterranean diet filled with fruits, vegetables, and beans, while averaging no meat (including fish), eggs,2100 or dairy on a day-to-day basis, had comparable short-chain fatty acid levels to vegans, even though the Mediterranean diet adherents weren’t completely plant-based all the time.

We’re slowly losing more and more of our microbes with every generation, placing some of our good bacteria at risk for extinction.2108 It may be a case of use it or lose it. “You just might consider choosing a salad at lunch today or an extra serving of beans at dinner,” one microbiologist commented. “Future generations may thank you, too.”2109

MAC is another name for prebiotics, primarily the fiber and resistant starch that fuel our gut flora, and is one reason why you can get an increase of nearly two grams of stool for every one gram of fiber: You’re boosting bacterial growth.2122 When we eat a whole plant food like fruit, we’re telling our gut flora to be fruitful and multiply.

For example, swap out meat for the same number of calories of whole grains, and people lose more weight. The noted increase in microbial diversity may be one of the factors contributing to the extra weight loss.2131

The Three Ps for gut health restoration are prebiotics, polyphenols, and probiotics.2132 Polyphenols are a class of phytonutrients (health-promoting plant compounds) that have long been investigated as potential candidates to explain some of the benefits of better diets against disease.2133 Polyphenols are produced by plants to protect themselves,2134 and we may be able to expropriate and commandeer them for the same purpose.2135

According to a national dietary survey, those who eat beans tend to be healthier and have less obesity risk, lower body weight, and smaller waist sizes.2304 This finding has been used to explain what’s known as the Hispanic paradox: Despite higher poverty rates and disparities in health care and education,2305 Hispanic Americans tend to live longer than everyone else.2306 Hispanics have a 24 percent lower risk of premature death, thanks to lower risks of nine of the fifteen leading causes of death, including notably less cancer and heart disease.2307

What’s powerful enough to overcome lower socioeconomic status, education level, health literacy, insurance coverage, and disproportionate employment in high-risk occupations?2308

we’ve known for more than thirty years that meals featuring beans can disproportionally delay the return of hunger.2322 Does this then translate into reduced caloric intake throughout the day?

Researchers compared patties made with fava beans and split peas to protein-matched patties made out of meat. The title of the study gives it away: “Meals Based on Vegetable Protein Sources (Beans and Peas) Are More Satiating Than Meals Based on Animal Protein Sources (Veal and Pork).”

The researchers suggested this may help explain why intake of animal protein has been associated with subsequent weight gain, but consumption of plant protein hasn’t.2326 Beans are free of the baggage inherent to animal protein sources, such as saturated fat and cholesterol, and instead offer a bonus in the form of fiber, which likely explains their satiety benefits.2327

What was discovered was that eating legumes could benefit your metabolism hours later 2330 or even the next day.

Eat lentils for dinner, and eleven hours later, your body reacts differently to breakfast.2331 Even when made to drink straight sugar water the next morning, your body is better able to handle it. At the time, the researchers dubbed it the “lentil effect,” but subsequent studies found chickpeas appear to work just as well. It has since been christened the “second meal effect.”2332

This second-meal effect can include changes in appetite. Eat half a can of brown beans at dinner, and you feel less hungry after breakfast the next day than had you instead eaten the same number of calories in non-bean form the night before.2333

There’s a reason legumes have earned the hallowed distinction of being officially recognized in the federal dietary guidelines as belonging to both the vegetable group and the protein group. They’re loaded with protein, iron, and zinc, as you might expect from other protein sources like meat, but legumes also offer nutrients concentrated in the vegetable kingdom, such as fiber, folate, and potassium.

Fearful of flatulence?

The bottom line (no pun intended) is that most people either don’t experience any gastrointestinal side effects after adding beans to their diets or the symptoms dissipate within the first few weeks.2373

We were built for gluttony. It’s a hedge against times of scarcity. Stumbling across a rare bounty, those who could stuff themselves the most to build up the greatest reserves would be most likely to pass along their genes. You might say it was the survival of the fullest. So we are hardwired to eat not just until our stomachs are full but also until our entire digestive tracts are occupied. Only when our brains sense food all the way at the end of our lower intestines may our appetites dial down fully.

A traditional Mediterranean bean-and-vegetable stew would be anti-inflammatory, low on the food chain, and high in fiber, trapped water, and veggies, have a low glycemic load and insulin index, be free of habit-forming ultraprocessed foods, and could be low in added fat, sugar, meat, salt, and refined grains.

Diets don’t work almost by definition. Going on a diet implies that, at some point, you will go off the diet. Short-term fixes are no match for long-term problems.2421 Lifelong weight control requires lifelong lifestyle changes.

A vegan diet, for example, can fail at this criterion, as it lacks vitamin B12, which is not made by plants but by microbes that blanket the earth. In today’s sanitized modern world, we now chlorinate the water supply to kill off any bacteria, so we don’t get a lot of B12 in our water anymore—

why B12 supplements or B12-fortified foods are critically important for anyone adopting a plant-based diet.2427

The hook for low-carbohydrate diets that may explain their recurring popularity since the 1860s is the rapid water loss that can accompany them.

Put people on a ketogenic, eight-hundred-calorie-a-day, low-carbohydrate diet, and they lose ten pounds in ten days, compared to only six pounds lost on the same number of calories of a higher-carb diet.

Same calories, yet four more pounds gone. What the bathroom scale isn’t telling you, though, is that those fo...

When you eat carbohydrates, your body bulks up your muscles with glycogen for quick energy. Eat a high-carb diet for three days, and you may add about two pounds of muscle mass on your arms and legs.2432 Those glycogen stores drain away on a low-carb diet and pull water out with them. The ketones also need to be flushed out of the kidneys on a ketogenic diet, accounting for the diuretic effect.2433

The thrill of seeing the pounds drop so quickly on the scale, though, keeps many keto crazy. When the diet fails, the dieters often blame themselves, but the intoxication of the initial rapid weight loss may tempt them back. It’s like getting drunk again after forgetting how terrible the last hangover felt. This has been dubbed the false hope syndrome.

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.

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

Ironically, one of the healthiest eating patterns, an exclusively plant-based diet, is perhaps the most life-threateningly incomplete, lacking B12, a vitamin made by bacteria, as I mentioned earlier.

In our modern sanitary world, vitamin B12 is found reliably only in animal products, supplements, and B12-fortified foods. Vegetarians and vegans are recommended to take supplements containing at least 50 mcg of cyanocobalamin (the most stable form2452) a day or at least 2,000 mcg once a week2453 (or brush twice daily with a B12-fortified toothpaste2454).

A plant-based diet is defined as an eating pattern that minimizes the intake of meat, eggs, dairy, and processed junk and maximizes consumption of whole plant foods, such as fruits, vegetables, legumes (beans, split peas, chickpeas, and lentils), whole grains, nuts and seeds, mushrooms, and herbs and spices.

Plant-based is often confused with vegetarian or vegan, but it can have very different health implications. Vegetarian (meat-free but may include eggs and dairy) and vegan (free of any animal-derived ingredients) diets may exclude animal products for religious or ideological reasons without necessarily focusing on healthy choices.

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,

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 pla...

Which eating pattern contains the most anti-inflammatory foods? Which is cleanest, the lowest in potentially obesogenic pollutants? Which diet is highest in fiber- and water-rich foods, yet lowest in addictive and processed foods, glycemic and insulin loads, calorie density, fat, meat, refined grains, salt, and sugar? Which is friendliest to our microbiomes, satiating, and rich in fruits, vegetables, and legumes, while, at the same time, is safe, sustainable, nutritious, and healthy?

It should come as no surprise that the most successful intervention to date is a whole food, plant-based diet.

A key difference between plant-based nutrition and more traditional approaches to weight loss is that people are encouraged to eat ad libitum, which is, as I’ve noted, Latin for at one’s pleasure. In other words, people on a healthy enough plant-based diet can eat as much as they want. No calorie counting, no portion control—just eating. The strategy is improving the quality of the food rather than restricting the quantity of the food.

The largest such study, which involved more than ninety thousand people, found that the more plants people ate, the lower their weights seemed to drop.2466

Only those eating purely plant-based diets were, on average, at an ideal weight with an average BMI of 23.6.2468

When whole plant foods made up about 40 percent of the diet, weight gain tended to decline with age rather than creep up.2470 Although 40 percent might not sound like a lot, because unprocessed plant foods tend to be so low in calorie density, getting 40 percent of your calories from whole plant foods may mean they take up 75 percent of your plate.

Every additional year of eating purely plant-based is associated with a 7 percent drop in obesity risk among adults.

plant-based equivalents like veggie burgers were not, and whole plant foods like grains, beans, and nuts appeared to be protective.2473

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.

Those randomized to eat purely plant-based lost more weight than those just avoiding meat, as well as those eating pesco-vegetarian, semi-vegetarian, or full omnivore. By the end of the six-month study, those randomized to eat a completely plant-based diet lost twice as much weight compared to those who ate any fish or other meat, with 7.5 percent of their body weights lost, compared to about 3 percent.

That may only translate into a few pounds of steady weight loss a month, but, again, this was achieved without added exercise, calorie counting, or portion control. Subjects on the plant-based diet were instructed to eat however much they wanted, whenever they wanted. That’s the kind of diet one can stick to long term.

Those who follow a whole food, plant-based diet for years can lose dozens of pounds.2500

Dr. Diehl put it best when he said: As a society, I think we are largely at the mercy of powerful and manipulative marketing forces that basically tell us … what to eat.… Everywhere we look, we’re being seduced to the “good life” as marketers define it, but … this so-called “good life” has produced in this country an avalanche of morbidity and mortality [disease and death].… What I would like to see in America is not this “good life” but the “best life.” The best life is a simpler lifestyle—one characterized by eating more whole foods, foods-as-grown.2515