How Not to Diet: The Groundbreaking Science of Healthy, Permanent Weight Loss

by Michael Greger

All that extra fat just spiked the calorie density, so all of a sudden, eating the same amount of food meant inadvertently eating a lot more calories.

Processed foods with reduced fat claims on the front of their packaging are often so packed with sugar that they may have the same number of calories per serving as a higher fat product.

Mushrooms are a great way to swap out calories and swap in flavor. They only have about one hundred calories per pound,1754 so incorporating them into our meals can certainly lower calorie density,

The largest study of those eating plant-based diets found that American vegetarians tend to weigh about twenty-five pounds less than those who eat meat.

In the same vein, vegans are forty pounds lighter on average than those who eat conventional diets,1803 but that doesn’t mean that cutting out meat, dairy, and eggs will necessarily make you lose forty pounds. Those who eat healthier also tend to live healthier, so it’s not necessarily the diet per se. Maybe vegans eat out less and work out more. To see if meat has an independent effect on obesity, we need to control for both dietary and nondietary factors.

Over a ten-year period, the amount of weight gain associated with eating more than seven servings of meat a week (compared to those averaging less than about one serving of meat every other day) was the same as the amount of weight lost by women who walked or men who jogged or ran four or more hours a week.

The EPIC researchers also found total meat consumption linked to increased weight gain, even at similar caloric intakes. They concluded: “Our results are therefore in favor of the public health recommendation to decrease meat consumption for health improvement.” The surprise, though, was that poultry appeared to be the most fattening. Consumption of poultry—mostly chicken—was associated with three times the weight gain compared to red meat like beef,

There’s a common misperception that switching from red meat to white meat lowers cholesterol, but when it was actually put to the test, no significant improvements were noted when people swapped beef, veal, and pork for chicken and fish.

When the meat industry funded an obesity study on chicken, they pitted it against “cookies and sugar-coated chocolates.”1824 This is a classic drug industry tactic: Make your product look better by comparing it to something known to be substandard.

The blood of patients who had experienced a heart attack or stroke was compared to the blood of those who hadn’t, and that’s how TMAO, short for trimethylamine oxide, was identified.1832 The more TMAO people had in their blood, the more likely they were to go on to suffer a heart attack, stroke, or otherwise die prematurely.1833 Where does TMAO come from? Just as short-chain fatty acids are produced by good bacteria in our gut when we eat fiber, TMAO originates from bad bacteria in our gut when we eat lots of choline (concentrated in eggs, but also lecithin supplements) or carnitine (concentrated in meat, but also some energy drinks).

This same phenomenon happens in plants too.1846 If you take two genetically identical plants and grow one in the sun and the other in the shade, the sun-grown plant will produce seeds that grow better in the sun, while the shaded plant will produce seeds that grow better in the shade—even though the two plants are genetically identical.

Take chicken, for example. In 1896, the USDA determined chicken was about 23 percent protein and less than 2 percent fat by weight,1857 which is even leaner than some wild game like venison.1858 Today, with ten times the fat, chicken has 1,000 percent more fat than it did just over a century ago.1859 These days, more than 70 percent of the calories in chicken may come from fat.

When proponents of low-carb diets demonize carbohydrates, public health advocates are quick to point out that it’s the source that matters—carbohydrates can mean everything from lentils to lollipops.

One of the most dramatic changes in our diets has been the skyrocketing intake of salt. For most of human existence, we were only getting the pinch of salt a day naturally found in whole foods.1902 Now, thanks mostly to processed foods, we’re exposed to ten times more than our bodies were meant to handle.

When people were switched to a low-salt diet, the levels in their blood of the gut hormone ghrelin dropped, and when shifted to a high-salt diet, their ghrelin levels shot up.1927 Ghrelin, the so-called hunger hormone I discussed in the High in Fiber-Rich Foods section, is the target of attempts by drug companies to create an anti-obesity vaccine,1928 but we may be able to help block its action naturally by lowering our sodium intake.

To their credit, low-carb and paleo diet advocates identify insulin as playing a role in the obesity epidemic, but they often don’t appear to recognize the broader scope of insulin triggers. Since carbs increase insulin, the argument goes, we should eat lots of meat, which is just fat and protein with zero carbs. That wouldn’t cause an increase in insulin, right? Wrong. We’ve known for more than a half century that if you feed people a steak, their insulin levels go

It turns out meat protein causes almost exactly as much insulin release as pure sugar.

Those eating plant-based diets average significantly lower insulin levels and have less insulin resistance, even compared to nonvegetarians at the same body weight.1969,1970 In fact, those who eat meat have up to 50 percent higher insulin levels in their bloodstreams.

After ten weeks of hard-core workouts and weight loss on the paleo diet, however, the study participants’ LDL cholesterol still went up—and it was even worse for those who started out the healthiest. Those who started the study with optimal levels (under 70) had a 20 percent elevation in this leading risk factor for heart disease, our number one killer.

The researchers concluded that “the Paleo diet’s deleterious impact on blood lipids [fats] was not only significant, but substantial enough to counteract the . . . improvements commonly seen with improved fitness and body composition.”

Plant proteins tend to be lower in the branched-chain amino acids (BCAAs) and the sulfur-containing amino acid methionine, which both have been associated with insulin resistance.

Amino acids are the building blocks of proteins. There are about twenty different kinds,2001 similar to the number of letters in the alphabet. Just as different sentences can be made from different combinations of letters, different proteins are made from stringing together different sequences of the various amino acids.

Three of the amino acids—leucine, isoleucine, and valine—have fatty side-chains that branch off from their central structure and are thereby referred to as branched-chain amino acids.

Indeed, just like you can make someone insulin resistant by infusing fat into their bloodstreams, you can do the same thing by infusing amino acids.2015 Down a protein drink of just straight whey and water, and it can cause insulin resistance within hours.

Take some omnivores and put them through even just a “48-hour vegan diet challenge,” and you can produce significant improvements in metabolic health.

The recommended dietary allowance for protein is about 50 grams a day (46 for women, 56 for men).2019 The researchers took men who were averaging twice that—112 grams, which is about the average of what many American men get2020—and randomized them down to 64 grams of protein a day. They were still getting more protein than they needed. The levels of branched-chain amino acids circulating in the lower-protein group dropped as suspected, but did they lose weight? Both diets were designed to have the same number of calories, so six weeks later, both groups should weigh the same, right? The body weight and fat mass of the regular protein group didn’t change, but the lower protein group lost about six pounds.

The human colon has been considered the most biodense ecosystem in the world, meaning there’s more life concentrated in our colons than anywhere else on Earth.

Many probably think that stool is composed primarily of undigested food, but most of it—about 75 percent—is pure bacteria.2044 Trillions and trillions of them—about half a trillion per teaspoon, in fact.

“More bacteria live and work in one linear centimeter of your lower colon than all the hu...

According to the FDA, animal agriculture now feeds about thirty million pounds of antibiotics to livestock every year,2054 four times the amount sold to treat human infections.

It can take as much as a half pound of antibiotics to produce just one pound of salmon,2059 for example, which helps explain why the researchers found most of the samples from common seafood in the United States tested positive for trace amounts of antibiotics.

Ounce for ounce, the colon contents of those eating more plant-based diets have nearly three times the capacity to form short-chain fatty acids.2083 In this way, eating healthfully not only provides more raw materials for short-chain fatty acid production but improved microbial machinery to churn out more of it. In contrast, putting people on a low-carb diet can slash short-chain fatty acid production by up to 75 percent.

Remarkably, however, all of humanity appears to cluster toward one of two broad categories called enterotypes.2089 Enterotypes are not like blood types, which put us distinctly into specific immutable categories.2090 Instead, our gut flora exist in more of a continuous gradient with tendencies to drift one way or another. And when it comes to our gut flora, there are apparently two types of people in the world: those who grow mostly Bacteroides species and those who grow mostly Prevotella.

The enterotype data suggest there are two types of colon ecosystems, so you can split humanity into people whose guts grow a lot of Bacteroides-type bacteria and those whose guts are better homes for Prevotella species.

The richest microbiomes ever recorded were those of the Yanomami tribe in the Amazon jungle who had no previous contact with the modern world.2103 Traditional societies tend to have more diverse gut flora in general, and the key is thought to be their extraordinary fiber intakes, which can reach 120 grams a day,2104 nearly eight times the American average.

Protein, carbs, and fat are macronutrients because we eat them by the gram each day, whereas vitamins and minerals are micronutrients, as we may only get thousandths or even millionths of a gram a day.

For example, three cups of coffee a day can significantly raise Bifidobacteria levels in the gut within three weeks.2155 Adding milk, though, may block some of the benefits.

We know that Big Pharma is infamous for this; industry-funded studies that yield negative results are quietly shelved and buried, so all your doctors get to read are the glowing reports.

Still, put all the studies on treating obesity with probiotics together, and overall, a small loss in body weight was found—though there was no significant loss of body fat, which is what we really care about when it comes to weight loss.

This suggests raw fruits and vegetables may not only be a source of prebiotics—that is, fiber—but also a source of probiotics.2177 Some may even help us reap the rewards.

Currently, just such a study is under way at Harvard: Stools from lean individuals are being transplanted into obese individuals to see if they suddenly start to lose more weight.2203 Stay tuned.

What we eat can change the composition of our gut flora—for good or for ill—within twenty-four hours.

What about obesity? Wouldn’t it be a refreshing change from all the restrictive “eat less” messaging to hear a positive “eat more” message? Sometimes proscriptions can backfire and make people want what’s been labeled taboo even more2217—just ask Eve. Can we flip this “forbidden fruit” effect on its head and start encouraging more fruit?

fruit juice can carry the same sugar load as soda2234 and the same amount of fiber: zero. Even “high pulp,” “extra pulp,” and “most pulp” orange juices are not significant sources of fiber. It’s all pulp fiction.

In foods, there are intracellular calories and extracellular calories—in other words, calories that are confined inside cells and calories that are free to be absorbed directly. Processed plant foods like fruit juice, refined grains, and sugar are letting it all hang out, and their calories are free for the taking. In contrast, all the calories in whole plant foods are not only trapped inside cells—they’re also trapped inside cell walls.

A study in Norway tested out a free fruit program among schoolchildren. Compared to control schools, a year of free fruit for ten- to twelve-year-olds resulted in a 40 percent lower prevalence of being overweight seven years later.

The recommended minimum number of daily servings of fruits and vegetables a day is seven to thirteen, but most Americans don’t even get five.

Does it matter when you eat your fruits and vegetables? In my Negative Calorie Preloading section that’s coming up in part IV, I explore the benefits of making them the first choice for your first course. There’s even a public health campaign in Japan called “Eat Vegetables First at Meals.”2291 Just changing the order of foods you eat can have meaningful metabolic impact. Compared to the exact same meal eaten in a different order, eating vegetables first can decrease blood sugar and insulin excursions in diabetics2292 and prediabetics,2293 resulting in significantly better blood sugar control over the long term.

2329 What was discovered was that eating legumes could benefit your metabolism hours later2330 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.

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.