How Not to Diet

"If all consumers exercised, obesity wouldn’t exist." But is movement truly the root of our weight struggles—or could it be what we eat? Michael Greger explores the modern diet's real culprit.

1. Obesity: A Normal Reaction to an Abnormal Environment

Our biology was designed to thrive in food-scarce environments. Historically, humans survived by eating calorie-dense foods when they could find them, as food was often unpredictable and scarce. This ability to store fat was essential for survival.

However, in today’s world, food scarcity has been replaced by food overabundance. Highly processed, calorie-rich items are now everywhere. Our innate attraction to calorie-dense foods, developed for survival, makes us crave chocolate, fatty snacks, and sugary drinks instead of lettuce or cucumbers. These unnatural, calorie-heavy foods overwhelm our instincts and lead to weight gain.

Obesity, therefore, is not an individual's failure but a predictable response to an environment overloaded with unhealthy options. It’s our human biology reacting naturally to an artificial setting.

Examples

• One in three adults in the US is now obese, compared to one in 30 a century ago.
• Processed items like chocolate chip cookies can deliver thousands of calories per pound, far surpassing natural foods like bananas.
• Children have an innate preference for calorie-dense foods like potatoes over low-density options like berries.

2. Modern Foods Pack Too Many Calories

Starting in the 1970s, the food industry underwent a transformation, creating processed, ready-to-eat items that were cheap, accessible, and loaded with calories. This shift coincided with a sharp rise in obesity rates, as the environment made overconsumption far too easy.

By 2000, the United States was producing 3,900 calories a day per person. This was a huge jump from traditional, home-cooked meals of the 1960s, which often used basic ingredients and required preparation. The advent of calorie-laden snacks like Twinkies turned rare indulgences into daily staples.

The disconnect lies in the profitability of processed products. Companies like PepsiCo profit more from junk food than healthy alternatives, creating a system where the cheapest and most profitable foods happen to be the unhealthiest.

Examples

• America’s obesity spike began in the 1970s alongside the rise of processed snack foods.
• Frito-Lay products generate as much as 10% of a supermarket's profits, even though they represent only 1% of sales.
• Americans now consume 500 more daily calories than previous generations, mirroring a 500-calorie average weight gain.

3. Fiber Helps Shed Extra Weight

Fiber is overlooked but plays a key role in weight management. By increasing fiber intake, people feel fuller faster, absorb fewer calories, and naturally reduce their calorie consumption without even realizing it. High-fiber foods are less calorie-dense but very filling.

For instance, eating an apple versus drinking apple juice shows how fiber impacts fullness. The whole fruit keeps you feeling satisfied, while the juice lacks fiber and leaves you craving more. Fiber traps some calories before the body can absorb them, functioning like a natural calorie discount tool.

Studies show that simply adding 14 grams of fiber daily can lead to a weight loss of about 4 pounds in four months—no major diet change needed.

Examples

• People eating whole-wheat bread excrete more calories from fat than those eating white bread due to fiber.
• Eating five cups of apple slices is far more filling—and no more caloric—than a bottle of apple juice.
• Legumes like beans and lentils are fiber-rich and effective at curbing hunger.

4. Low Glycemic Foods Reduce Fat Storage

Foods that cause a sugar spike, such as white bread or cornflakes, leave you feeling hungry and can disrupt your metabolism. These foods, with a high glycemic load, promote overeating later as well as slower calorie burning when at rest.

Low glycemic options like oatmeal or chickpeas digest more slowly, helping control appetite and reducing fat-storing tendencies. When we keep blood sugar steady with these smarter food choices, it helps maintain a stable weight-loss journey without constant cravings.

Avoiding foods like potatoes and shifting to legumes or non-starchy vegetables can offset the temptation of high-sugar snacks and lead to sustainable fat burning.

Examples

• Kids eating sugary cereals consumed more calories at lunch than those eating oatmeal with the same calorie count.
• Studies reveal that high-glycemic eaters face an 80-calorie metabolic slowdown—a potential weight-gain trigger.
• Low-glycemic legumes like chickpeas can reduce calorie consumption by nearly 200 at the next meal.

5. Fat Is Weight-Gain Fuel

Fat is calorie-dense and easily stored by the body compared to carbs or proteins. While some promote high-fat diets as solutions, they often overlook that historically, humans consumed only about 10% of calories from fat in natural diets.

Modern “low-fat” standards, such as today’s lean ground beef, still contain much more fat compared to traditional eating patterns. Yet truly low-fat diets—shy of 10%—have been proven to result in noticeable weight loss. By cutting out oils and fats, people can dramatically alter their calorie consumption and store less body fat.

Examples

• Dr. Dean Ornish’s participants halved their fat intake and lost an average of 24 pounds in one year.
• Wild game, which is naturally lean, contains less than 15% fat compared to processed red meats today.
• Low-fat cooking substitutes, like using broth instead of oil, help cut hidden calories.

6. Added Sugar Is the Silent Weight Driver

We’ve gone from consuming 4 pounds of sugar a year during the Revolutionary War to over 50 pounds now. This daily sugar overload isn’t just nutritionally empty—it’s directly linked to overeating later on.

By eliminating added sugars for even two weeks, cravings diminish almost completely. Those who ditch sweetened products find it easier to maintain their eating routine and naturally slim down.

Reducing added sugars to less than 5% of daily calories is achievable and, in the long term, sustainable for good health.

Examples

• Kids served high-sugar cereals ate 77% more than those served low-sugar options.
• Cutting sugary drinks can reduce a child’s calorie intake by 235 a day.
• Studies show that sugar abstinence rewires taste preferences after just one week.

7. Replace Quantity with Quality: Calorie Density Matters

Eating smaller portions isn’t the only way to manage calories. Lowering calorie density—by including water-rich and nutritious items like vegetables and fruits—can be even more effective.

Our bodies are good at recognizing food volume, not calorie content. By filling up with broccoli or zucchini rather than oil-packed foods, we stay full but eat less overall, without effort or deprivation.

Swapping calorie-dense ingredients, like cream sauces, for lighter options, like tomato-based sauces, significantly impacts calorie consumption.

Examples

• Participants eating apples lost weight compared to those eating equivalent-calorie oatmeal cookies.
• Celery, with 95% water content, lets you eat more without gaining fat.
• Even small swaps, like replacing nuts with fresh produce, lead to calorie savings.

8. Legumes Are the Secret Weapon

Legumes offer dual benefits—they’re nutrient-packed and incredibly filling. They’re versatile enough to replace higher-calorie, less satiating meats while also curbing hunger throughout the day.

Research shows that legumes like beans or lentils lead to greater weight loss compared to many other foods because they help reduce overall caloric intake, all while improving digestion and heart health.

Preparing legumes is simpler than expected, especially if using canned options or quick-cooking varieties like lentils.

Examples

• Eating legumes helped participants lose an inch off their waistline in three months.
• Chickpea eaters consumed nearly 200 fewer calories in subsequent meals compared to bread eaters.
• Legume diets show faster weight loss rates than whole-grain comparisons.

9. Embrace Plant-Based Eating for Long-Term Success

A plant-based diet focuses on fruits, vegetables, legumes, and whole grains while limiting processed and animal-based foods. Unlike fad diets, it offers measurable health benefits without strict portion control.

Historical human diets were largely plant-forward, suggesting our systems thrive on simple, unprocessed foods rather than artificial substitutes. Returning to these basics is not only natural but effective for weight loss and overall health.

Examples

• Plant-based dieters can shed weight without restricting portions or tracking calories.
• Whole-plant eating avoids risks tied to low-carb diets, such as heart disease.
• Replacing fatty meals with plant-based ones provides unlimited volume with fewer calories.

Takeaways

1. Add legumes to your weekly meals—simple dishes like lentil curry or bean salads make healthy eating accessible.
2. Strive for low-calorie density by doubling up on fruits and vegetables to fill your plate.
3. Kick added sugars for two weeks to reset cravings and reduce excess calorie intake effortlessly.