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

by Michael Greger

Researchers acquired seventy-six samples of different kinds of meat, both organic and conventional, and quantified their levels of contamination with thirty-three different persistent toxic pollutants. No sample was completely free of industrial toxins, which is to be expected given how polluted our world has become. What was surprising, though, was how minimal the differences were between organically and conventionally produced meats. In some cases, organic was inexplicably worse. Whether choosing conventional or organic meat, the researchers concluded that the current pattern of meat consumption exceeded the maximum tolerable safety limits either way.

In 1869, a patent was taken out on a new substance to replace elephant ivory in the production of billiard balls, and the plastics industry was born.1157 What started as a conservation-minded measure has turned into an environmental calamity.

It is inevitable that we’ll ingest at least some microplastics when we eat seafood, particularly when the entire animal is consumed, such as with sardines.

Ironically, one of the food components that produces the most dramatic effects is something that initially appeared to be the most inert of dietary constituents: fiber.1174 In fact, telling people to increase their intakes of fiber-rich foods may actually be one of the single most effective pieces of advice for weight loss.

Fiber seems so, well, boring. By definition, fiber is indigestible. Since it can’t be absorbed into the body, it just stays in our gut to bulk up our stool. This is not to belittle the importance of bowel regularity. If just half the adult population ate three additional grams of fiber a day—only a quarter cup of beans or a bowl of oatmeal—we could relieve enough constipation to save billions in medical costs a year.

researchers compared how long it took for a meal that included higher-fiber foods—whole-wheat pasta with puréed fruits and vegetables—to leave the stomach compared to a meal with the same volume and same calories, but made from white pasta and fruit and vegetable juices. The fiber-depleted meal was out of the stomach forty-five minutes earlier than the meal with the fiber intact.

Drip some SCFAs onto L cells, and they start churning out PYY and GLP-1. You can do this in a petri dish1228 or in a person, either by infusing their rectums with an SCFA enema1229 or the old-fashioned way of feeding people fiber1230 or, even better, fiber-rich foods.1231 These hormones then get released into the bloodstream where they can shoot right up into the appetite center of the brain and turn down our cravings.1232

One of the most fascinating studies that has been done in this area involves putting people into an fMRI machine that measures real-time brain activity. Subjects were shown a high-calorie food such as a donut, and the reward centers in their brains instantly lit up compared to when they were shown a low-calorie food like cucumber slices. What happens if you repeat the experiment, but this time, after secretly delivering SCFAs directly into their colons? The subjects reported the high-calorie foods seemed less appealing, and this was matched by decreased activity in some of the reward centers in their brains, whereas their brains continued to react about the same to the less-craveable foods.

Eat fiber-rich foods, though, and our good gut flora take the fiber we eat and churn out molecules that calm our cravings.

“increasing consumption of dietary fiber with fruits, vegetables, whole grains, and legumes across the life cycle is a critical step in stemming the epidemic of obesity.”

Researchers in Sweden fed people beans for dinner, and, by the next morning, after their friendly flora had also had a chance to feast, their satiety hormones like PYY were up, their hunger hormone ghrelin was down, and they reported feeling less hungry.

Fewer than 3 percent of Americans reach even the recommended minimum daily adequate intake of fiber.1272 There’s so much fuss about protein, but for that, the stats are reversed: More than 97 percent of Americans get enough protein, but more than 97 percent of Americans don’t get enough fiber.

Sadly, the average fiber intake in the United States has failed to improve in recent years despite ongoing public health messaging about its importance.1282 One problem may be that people just don’t know what fiber is. More than half of Americans surveyed think steak is a significant source of fiber.1283 However, literally by definition, fiber is only found in plants.1284 There is zero fiber in meat, dairy, or eggs and typically little or no fiber in junk food. Therein lies the problem.

Those of us who may be a little smug about our hearty intake of fruits and vegetables need to realize that fruits and leafy veggies are the poorest whole-food sources of fiber. Why? Because they’re 90 percent water. Root vegetables have about twice as much on a per-weight basis, but the fiber superstars are whole grains and legumes, which include dried or canned beans, split peas, chickpeas, and lentils.

In general, when it comes to water-rich foods, most whole plant foods float up near the top, most animal foods fall somewhere in the middle, and most processed foods sink to the bottom.

The impact of carbs on the body depends on their source. Kidney beans and jelly beans are both rich in carbs but can have diametrically different impacts on our bodies. Bread made from the exact same ingredients as pasta causes nearly twice the blood sugar spike, leading to nearly three times the insulin release as the same number of carbs consumed in noodle form.

Many high-glycemic foods are highly processed and fiber-depleted, so when you swap them for low-glycemic foods like beans and fruit, you’re doing more than just changing the glycemic load.

In fact, fat intake has not fallen; it’s gone from an estimated average of 743 daily calories of fat in the 1970s to 747 in the latest national survey.1362 The availability of added fats and oils rose more than 50 percent, from 52.5 pounds per person in 1970 to 82.2 in 2010.1363

The debate is often framed as fat versus carbs, but health-wise, the term carbs is practically meaningless, as it could refer to black beans or Blow Pops.

Many people see the words low fat and assume that means the product is healthy overall.

Deliberately distracting attention away from negative qualities or the overall vacuity of nutritional content has a name: nutri-washing.

Food, not nutrients, is the fundamental unit in nutrition.1379 The source of fat is likely more important than the amount of fat.

let’s not forget that the healthiest foods don’t have any nutrition labeling on them at all. In the grocery store, you’re more likely to see “healthy” claims adorn Apple Jacks than apples.

It’s not the fat per se but rather the consequent increase in calories per mouthful because fat can sneak lots of calories into a relatively small space.

If I hooked you up to an IV and, unbeknownst to you, dripped 1,300 calories of sugar into your veins, studies show your body somehow “tastes” how sweet your blood has become, does the math, and turns down your appetite so much that you spontaneously eat about 1,100 fewer calories that day.1435 That’s a huge drop in intake, but your body sensed all those extra calories in your system and made you that much less hungry to compensate. Genius! But if I repeat the experiment with fat, we get a different result. Have 1,300 calories of fat secretly infused into your veins, and your body knows something is going on but doesn’t quite get the same picture as it did when you got those extra calories from sugar. So you only end up compensating by eating about 500 fewer calories that day.1436 Your body just doesn’t seem to register fat calories as well as sugar calories.

Eat a low-fat diet (11 percent calories from fat), and you burn more calories in your sleep than when on a high-fat diet (58 percent).

At rest, we burn about one calorie a minute, which is comparable to the heat produced by a seventy-five-watt light bulb.

Overeating on an 11-percent-calories-from-fat diet led to 620 more calories down the toilet every week than a same-calorie diet containing 58 percent calories from fat.

The researchers found that about 50 percent went straight into belly flab, 40 percent to their thighs, and most of the remaining went into visceral fat, the fat that’s buried around our major organs.

So, while we can certainly gain weight from eating carbs, it’s more from sparing our own fat from being used, rather than adding more fat directly.1462

Oleic acid, the primary monounsaturated fat found in olives, nuts, and avocados, is burned promptly about 20 percent more readily than palmitic acid,1475 the predominant saturated fat in the American diet, which is sourced mainly from meat and dairy.

there are four main components to calories out: resting metabolic rate, physical activity, the thermic effect of food, and fecal losses.

At first I was skeptical of oil-free cooking. So many of the dishes I made growing up started with sautéing garlic and onions, and how could you possible bake without fat? I was delighted to discover that cooking without oil is surprisingly easy. To keep foods from sticking in the pan, you can sauté in wine, sherry, broth, vinegar, or just plain water. The trick is to just use a little liquid at a time.

As revealed in an internal memo, the U.S. government apparently had a list of demands from Big Sugar that included the removal of all references to the science that WHO experts had compiled on the matter, as well as the call for the “deletion of all references to fat, oils, sugar and salt.”

The good news is that after stopping artificial sweeteners, your original balance of gut bacteria can be restored within a matter of weeks.

The industry is quick to point out that a calorie is a calorie, and an excess of calories from Coca-Cola would cause no more weight gain than the same excess of calories from carrots.1560 While this may be true in a tightly controlled laboratory setting,1561 it doesn’t take into account the appetite-enhancing effects of sugar.

Ever find yourself eating even when you’re no longer hungry and then continuing to eat even when you know you should stop? Taste engineers manipulate the salt, sugar, and fat contents of foods to achieve what’s referred to in the industry as the bliss point, the peak of craveability.

So which is worse: fat or sugar? The answer is both. As it turns out, opiate-blocking drugs work best not for sugary foods like jelly beans but for foods that combine sugar and fat.1629 The combination of sugar with fat creates a “hedonic synergy.”1630 Think ice cream, candy bars, and donuts.

The “sweet tooth” link to obesity may be more of a “sweet-fat tooth.”

If you follow people’s chosen diets, the best predictor of overeating and weight gain in children, adolescents,1633 and adults may be the selection of high-fat, high-sugar foods.

In nature, while there are foods that contain sugar (like fruit) and foods that contain fat (like nuts), sugar and fat rarel...

Food processing can increase both simultaneously, delivering high loads of concentrated sugar and fat, while, at the same time, stripping away fiber, protein, and water to maximize the rate of absorption.1638

In one sense, we have no control over most of the sodium we’re exposed to since more than two-thirds of sodium intake comes not from the saltshaker at home but from salt added to packaged foods and dishes in restaurants.

The underlying assumption is that palatable food equals unhealthy food, which is only true because the food industry has so deadened our palates with hypersalty, hypersweet, hyperfatty foods. The ripest peach in the world may taste sour after a bowl of Froot Loops.

It’s all about resetting our taste thermostats. The average life span of a taste bud cell may only be about 250 hours.1675 That means each of our taste buds could get replaced every ten days or so.

Drizzling just one tablespoon of oil on a dish adds 120 calories.1691 For those same 120 calories, you could eat about two cups of blackberries, a food with a low calorie density.1692 You could swig down that spoonful of oil and not even feel a difference in your stomach, but eating a couple of cups of berries could start to fill you up.

A handful of jelly beans has about sixteen times more calories than a handful of cherry tomatoes.

Most weight-loss diets focus on decreasing portion size, but we know “eat less” approaches can leave people feeling hungry and unsatisfied.1705 Shifting the emphasis from restriction to positive “eat more” messaging of increasing intake of healthy, low-energy-density foods may offer a more promising strategy.

We’ve been hardwired by eons of periodic scarcity to seek out the greatest caloric bang for our foraging buck.1712 In a primitive setting, that motivation would drive us toward picking the ripest fruits and digging up the starchiest roots, but now, that same biological drive compels us toward processed junk heaviest in added sugars and fats.

What if instead of having people eat less food overall, you have them eat more calorically dilute foods?