Summary of "How Not to Diet"
How Not to Diet by Dr. Michael Gregor shines a much-needed spotlight on myths and truths related to diets and weight loss. Built on a mountain of evidence from peer-reviewed nutritional research, Dr. Greger’s explanations and recommendations are as empirically based as it’s possible to be.
For a .pdf version of the summary, click here.
Quick facts
How Not to Diet is 608 pages long in paper format, but the prose is not dense. This book is actually easy to read if you’re motivated to learn about the topic.
There are 4,990 citations, and you can access the original research articles if you wish.
While the book doesn’t offer a single “diet” or a single set of rules, it doesn’t make strong recommendations and provides checklists and actionable information.
Summary of Section 1 – The Problem
Dr. Greger highlights that humans evolved for millions of years in an environment of scarcity. Our environment has changed to an abundance of available food, but our built-in bodily mechanisms for surviving periods of undernourishment have not. Today 70% of Americans are overweight or obese.
He answers the question, why did obesity begin to soar in the 1970s and 1980s?
Food preservation and packaging technologies made major progress during this time.
Federal subsidies of sugar, corn, and animal feed began.
Corporations became hyper-focused on shareholder value and short-term return for investors, leading to aggressive marketing and attractive packaging.
Dr. Greger reviews current-day solutions to the obesity problem and shares the success records and risks of each.
Liposuction – it can produce weight loss but almost never helps with accompanying chronic diseases.
Bariatric surgery – up to 25% of bariatric patients have to have a second operation to rectify problems from the first. Most patients maintain at least a 20% weight loss five years later, but the surgery and recovery are difficult, the required lifelong eating-habit changes are profound, and psychological effects of undergoing the procedure should not be underestimated.
Prescription drugs – most weight-loss drugs have been pulled from the market because of severe side-effects. Those that are still on the market have resulted in minimal benefits and undesirable side-effects.
Supplements – With a lack of government oversight, many supplements do not contain what the label says they do or contain traces of dangerous substances. No supplement has been found to be effective without undue health risks.
Policy approaches – Dr. Greger advocates for the government to use strategies similar to those used against tobacco and trans fats. He describes several attempts to regulate unhealthy food (such as sugary breakfast cereals) that failed when faced with highly-funded opposition from food industries.
Summary of section 2 – Ingredients for the Ideal Weight-Loss Diet
Dr. Greger covers 17 characteristics of diets that will help people lose body fat. After reading this section, I understood digestion better, especially the mechanisms in our bodies that signal “full.” The gist to losing weight effectively is to eat foods that will make you feel full physically and eat foods that work with your built-in chemical signaling system to either “eat” or “stop eating”
1. Anti-inflammatory
Chronic inflammation within the body perpetuates disease. Inflammation is our body’s reaction to unhealthy assaults on the body, including some foods. Processed foods and animal products, especially those with saturated and trans fats, are pro-inflammatory, while whole plant foods are anti-inflammatory. The most anti-inflammatory foods are turmeric, ginger, garlic, and green and black tea, but legumes, vegetables, and fruits also contain important anti-inflammatory compounds.
2. Clean
Many chemical pollutants that get into the food supply promote obesity. About 90% of food-borne pollutants comes in animal-derived foods. In addition to avoiding animal products, Dr. Greger also recommends prioritizing fresh or frozen vegetables over canned (which may contain BPA) and eating organic produce when possible.
3. High in fiber-rich foods
A high-fiber diet appears to be one of the most effective means of losing and managing weight. In the stomach, fiber fills you up. A gel forms around fibrous substances, which slows the food’s travel from stomach to intestine. It takes 45 more minutes for a fiber-rich meal to move from the stomach to the intestine than a fiber-poor meal.
In the colon, your good gut bacteria feed on fiber and use it to make short-chain fatty acids, which stimulate production of leptin, which lessens the appetite. We should aim for at least 30 grams of fiber per day. Whole grains and legumes provide the most fiber.
4. High in water-rich foods
Vegetables have the highest water content of all types of food. The more we chew, taste, and feel food in our mouths, the more our brains believe we’re filling up, even if the foods are full of water. Water inside foods has more of this filling effect than just drinking water does, because the water is trapped in the structure of the plant and thus requires more time and energy to be separated out from the rest of the food.
5. Low glycemic load
Carbohydrates that are digested quickly—like bread and candy—can increase our appetites, lower our metabolic rates, and decrease how much fat we burn. Unprocessed foods are the best for low glycemic load. Legumes and berries have been show to blunt the glycemic rush of the foods they’re eaten with.
6. Low in added fat
Dr. Greger reviews research that shows that when people eat an abundance of low-fat foods and avoid foods with added fats, they lose weight. Studies also show that our bodies are not good at registering fat calories and putting the brakes on our appetites when fats are consumed. Saturated fats (such as those in palm, coconut, and other oils; also in animal products) appear more likely to be stored as fat cells. For lasting weight loss, it’s important to cut down on or eliminate fatty meats, dairy, fried foods, greasy snacks like potato chips, and added oil.
7. Low in added sugar
Humans evolved to like the sweet taste of ripe fruit, and our innate preference for sweet foods extends now to white sugar and other refined sugars. Whereas ripe fruit is healthy for us, added sugars have been shown time and time again to contribute to weight gain.
8. Low in addictive foods
Salt, sugar, and fat—when extracted from whole foods and concentrated by modern production processes—can overstimulate the reward pathways in our brains and override our self-control mechanisms. Not all people exhibit addictive responses to such foods, but these processed foods have a similar effect on our brains as some addictive drugs. It can take a few weeks of abstention to reset our taste thermostats and weaken the addictive allure of processed foods.
9. Low in calorie density
Caloric density is the amount of calories in a gram of food. Usually it’s represented in tables and graphs as the amount of calories in a pound of food. The lower the caloric density of the food you eat, the more you can eat. Studies of low-calorie-density diets have found that people can reduce the amount of calories they need to eat and still achieve satisfaction and fullness. Vegetables, fruits, legumes, and unprocessed grains are at the “safe” end of the caloric density scale.
10. Low in meat
Controlling for all other dietary factors, researchers found that meat intake (especially poultry) correlates with higher weight (especially abdominal obesity) than a meatless diet. Meat also contributes to the proliferation of TMAO (trimethylamine oxide) in our blood, which is associated with heart attack, stroke, and higher weight.
11. Low in refined grains
Refined grains, especially white flour and white rice, are America’s number one source of calories. Substituting whole grains appears to lead to an increase in resting metabolic rate and increased calorie loss through the stool, which together can add up to 90 calories a day, or about 9 pounds a year.
12. Low in salt
Salt intake has been linked to excess body fat in numerous research studies. Salt may increase levels of the hormone ghrelin, which causes the sensation of hunger.
13. Low insulin index
Obesity can jumpstart a vicious cycle by leading to insulin resistance in the muscles, which leads to elevated insulin levels, which can cause more obesity. Eating less saturated fat can help break this cycle, as can eating foods with a low glycemic load. Meat, poultry, and fish cause excessive insulin release.
14. Microbiome Friendly
The trillions of bacteria living in our colon reflect our diet. The good gut bacteria love fiber and produce short-chain fatty acids in return, which help suppress the appetite. A diet of unhealthy processed and fiber-poor food encourages the growth of a type of bacteria that extracts even more calories in the colon than good bacteria do, so eating poorly is a type of double-jeopardy when it comes to weight control.
15. Rich in Fruits and Vegetables
For losing body fat, it’s imperative to get at least 7 servings of fruits and vegetables per day, and Dr. Greger recommends eating at least 9. Most Americans don’t get even 5 servings a day. In study after study, consumption of fruits and vegetables is associated with weight loss and lower weight. Note that juices (e.g., fruit juices) are not the same as whole fruit, since the fiber and other important parts of the fruit are not eaten.
16. Rich in Legumes
Only about 8% of Americans eat beans on any given day, but legumes are incredibly important for losing body fat. Legumes help you feel full, because they contain loads of fiber as well as protein. Soybean intake correlates the highest with weight loss over time, and the myth that soybeans can cause or accelerate breast cancer has been shown over and over not to be true. (See my post on soybeans here.)
17. Satiating
Humans have a strong instinct to feel full, so starving yourself or eating small, controlled portions will very likely fail in the long run. Because humans evolved in an environment where food was not abundant and easy to get at, our brains came to place a high value on salt, sugar, and fat. When we are tempted by food that is sugary or fatty, this deep instinct to fill up on high-calorie food overrides our basic appetite control system, which regulates appetite on the basis of energy reserves in the body. In other words, junk food messes with the mechanics of the chemical signaling in our body, so we might be more prone to eat when we’re not hungry.
Summary of Section 3 – The Optimal Weight-Loss Diet
In this section, Dr. Greger first describes four other factors that are critical for successful weight loss and maintenance.
1. Diet must be sustainable.
2. Diet must be safe.
3. Diet must be nutritionally complete.
4. Diet must be life-extending.
He then outlines the numerous research studies and meta-analyses that have shown that a plant-based approach to weight loss and long-term maintenance is significantly more effective than low-carb diets, including the ketogenic diet. He notes that “lifelong weight control requires lifelong lifestyle changes” and discusses at length the superiority of a plant-based diet for maintenance.
Summary of Section 4 – Weight Loss Boosters
Dr. Greger’s fourth section discusses further enhancements to eating habits that have been shown to promote weight loss and maintenance. The enhancements include self-monitoring, natural ways to suppress the appetite, optimal eating times and speeds, intermittent fasting, and many others. All of these have been shown in research to have an effect on weight loss or appetite suppression. I recommend reading the book to understand how each of them works. It’s difficult to do them justice in summary form. The recommendations come alive when you read the details.
Summary of Section 5 – Dr. Greger’s Twenty-One Tweaks
Building on the research discussion in Section 4 about enhancements, Dr. Greger boils down these recommendation to 21 easy-to-follow diet tweaks. His tweaks are meant as a complement to the Daily Dozen list, his previously published checklist of foods he encourages people to fit into their daily eating habits. I list the tweaks here, but again, I encourage you to read more about them in the book.
1. Preload with water
2. Preload with ‘negative calorie’ foods
3. Enjoy undistracted meals
4. Follow the 20-minute rule
5. Incorporate vinegar
6. Cumin
7. Black cumin
8. Garlic powder
9. Ground ginger and cayenne pepper
10. Nutritional yeast
11. Green tea
12. Stay hydrated
13. De-flour your diet
14. Front-load your calories
15. Time-restrict your eating
16. Optimise exercise timing
17. Complete your implementation intentions
18. Weigh yourself twice a day
19. Fast after 7pm
20. Get sufficient sleep
21. Experiment with mild Trendelenburg
Final word
The book overall is a fantastic read, and Dr. Greger and his co-author, Gene Stone, have done a great job making it approachable and enjoyable. I hope this summary has whetted your appetite for the whole book.