Calories

The human species evolved in an environment that provided few calories and that required a significant expenditure of energy to acquire those calories. As a result, our bodies are efficient in utilizing calories and have no limit in storing excessive caloric intake in the form of fat. Human beings may be hardwired to prefer sweets such as honey and ripe fruits since they are a calorie-dense source that requires a relatively low expenditure of energy to acquire. This would have been a useful trait in our days of being hunters and gatherers.

Certain foods require more of a metabolic cost to convert food to body fat. Complex carbohydrates can require 25% of their calories for metabolism in contrast to fats that only require 3%. For women, this may have been beneficial since they would, in times of plenty, store extra nutrients needed to subsequently feed a developing fetus or breast-feed a newborn. Today, few calories need to be expended to acquire large amounts of calorie-dense food. Given that satiety is mainly determined by food volume and not calories it is easy to increase calorie intake today. Food portions have increased dramatically at restaurants with greater emphasis on fatty foods (fried, creamed, or buttered) and sweetened drinks (soft drinks and juices with increased portion sizes). Today it is easy for a person to consume >1000 calories in a single meal. Finally stored fat has little effect on an individual’s appetite but can dramatically decrease activity levels leading to a vicious cycle.

Many of our weight loss efforts have been related to decreasing caloric intake through dieting. There are numerous diet strategies including low fat (Ornish), moderate fat (glycemic index or balanced reduction, eg Weight Watchers or Jenny Craig), and high protein (Atkins or South Beach). Different patients will have different degrees of success with different approaches. Studies that compare diets find that the single most important factor predicting success is the patient’s compliance with the diet. For this reason, there is no perfect dietary strategy. Patients should choose an approach that emphasizes foods they like, which may increase compliance for a longer period of time. Thus a carnivore may do better with a high-fat/-protein diet such as Atkins while an herbivore likely would do better on a moderate-fat menu such as Jenny Craig or Weight Watchers.

Dietary plans need to stress reduced/different caloric intake as a lifestyle change and not as a punishment that must be endured until one becomes skinny. The provider needs to stress the concept of healthy weight, not a fashionable weight. No matter what diet plan is followed the loss of 10% of body weight will positively impact comorbidities of hypertension, diabetes, and sleep apnea.

Just as hunting, gathering, and a caloric-scarce environment controlled weight in early man, an increase in physical activity is helpful in weight loss by increasing the expenditure of calories. However, most patients do not increase physical activity enough to truly generate weight loss. The sedentary lifestyle associated with computers, video games, and television is impacting negatively on the physical fitness of the country. Even physical education classes are being eliminated to provide more time for the “3 Rs.” Only students who participate in extracurricular sports benefit physically from school-based activities. Even if a patient engages in levels of physical activity that do not result in significant weight loss, it is still important for the physician to encourage patients to participate in physical activity such as walking for 30 minutes each day to help with conditioning and muscle tone. The key is to match activity to patient’s ability. A woman with a BMI of 40 is not likely to be successful taking up jogging but likely will be able to comply with walking. Again, our goal should be healthy, not skinny.