It takes time to change official government guidelines, and it requires extensive testing and positive results from several “randomized clinical trials.” These data are not yet available. Further, effective weight loss prescriptions are not “one size fits all.” Available data suggest that low carb diets work well for some, but not all, individuals. Until the underlying physiologic mechanism responsible for this variation in response to diet composition is understood, it is difficult to develop effective recommendations for weight loss.

Before World War II, it was well accepted that effective treatment of obesity, diabetes, and heart disease centered around limiting dietary carbs. Sadly, after the war, much of this knowledge and wisdom was lost. The new medical culture had different ideas that were not based on scientific data, but that nonetheless made their way into “official” guidelines.

About one-third of individuals are “carb intolerant.” This is the one-third of the population that suffers from overweight or obesity. It is important to realize that everyone’s body is doing EXACTLY what is it “supposed” to do, given the information it is being provided. In the case of people with high insulin, this information is “store fat.” The key to weight loss is to CHANGE the information you are giving your body. The best way to do this is to avoid consuming carbs, which will reduce the amount of insulin that is secreted. People with low insulin have a harder time storing fat, and are not as sensitive to carbs.

No. Exercise is great for getting fit, increasing muscle tone, boosting your immune system, combating depression, and enhancing a sense of well-being. However, exercise has limited value for weight loss. Exercise increases energy expenditure, which will increase appetite. In general, greater food intake will negate any calories burned during exercise. Your body knows how much energy it burns, and it will try to regain any lost energy by stimulating appetite.

No. Eating fat does not lead to increased body fat. Although this sounds logical, it isn’t true. Carbs (not fat) drive weight gain (fat gain). Eating carbs causes fat deposition. Eating fat actually causes weight loss, because your brain evolved to use fat as a signal for energy consumption. When you eat fat, your brain tells you to stop eating (it would be very hard to eat a pound of butter). Similarly, when you eat fat, your energy level increases, because fat is a wonderful fuel. You may find that you are more active when you are on a high-fat diet; that your metabolic rate stays high; and that you don’t feel cold all the time (a common side effect of low-calorie diets). When you eat fat, the feed-back loops that regulate food intake and energy expenditure work properly, and your brain and body know exactly how much you need to eat, and how active you can be to maintain a healthy body weight. In contrast, when you eat carbs, there is no mechanism to limit food intake (it is easy to eat the whole box of cookies). The obesity epidemic coincides with the proliferation of processed carbs in the grocery store, and the introduction of low-fat products. Low-fat products were not effective in preventing or reversing obesity.

Women evolved a need to have adequate energy stores to accommodate gestation and lactation. The hormone estrogen acts to increase insulin secretion and tissue response to insulin. As a result, women are very good at storing fat. However, estrogen also may act on the brain to affect appetite and spontaneous physical activity, actions that may explain why some women (not all) gain weight after menopause.

Yes. The low-carb approach is a high-fat diet, not a high-protein diet. Vegetarians will get all the fat they require from the same sources as carnivores: eggs, butter, olive oil, avocados, nuts, cheese, etc. Vegetarians can substitute eggs, tofu, and tempeh for meat. It is only necessary to consume 100 g protein per day. Some vegetarians may wish to incorporate a whey protein supplement into their diets.

No. Agriculture was developed ~10,000 years ago. This is a blink of the eye in evolutionary time. Our bodies are still not adapted to grain. The same is true for processed sugar. Although our ancestors probably ate some berries, these berries were high in fiber that limited how fast the sugar was absorbed. This is a vastly different scenario than consuming a sugary beverage. Humans have certain dietary requirements. For example, you have probably heard of “essential amino acids.” We cannot make some amino acids, and we have to get them from the diet, often animal products. Similarly, there are “essential fatty acids” that must be acquired from the diet. In contrast, there are no “essential carbohydrates.” Our liver is very good at making glucose, and is responsible for maintaining blood glucose in a normal range throughout the 24-h day. Humans do not need dietary sources of carbohydrates to survive.

No. Your body may have “learned” to use sugar as a fuel, but it also can learn to use fat. Once you are “fat adapted” you will have plenty of energy. This may take a few days. However, when you are fat adapted you actually will have MORE energy, because you will not be experiencing the energy slumps that are common in individuals with a high sugar diet.

After World War II, a misguided theory emerged that obesity was the result of “eating too much and exercising too little.” We now know that this is not true; in susceptible individuals, obesity results from a high-carb diet. If you cut the carbs, you do not have to count calories; your body will naturally adjust to the weight that is right for you.