It has become common knowledge that people in wealthier countries are getting fatter, especially so in the United States. American children are becoming weightier, and we see more people waddling down the street and flocking to fast-food restaurants where they gorge on fats, sugars, and salt.

There are many reasons why people get fat. First is opposition from nature. Switching to a healthy can be a shock to the body. After being used to eating unhealthy food, ingesting new nutritious foods can trigger allergies with effects such as a bad rash. The doctor then tells the patient to switch back to his old diet until the rash is gone, and then slowly convert to the healthy diet.

The physiological changes from a new diet can also create bad emissions. After eating more fruit and less meat, the skin and breath may smell like alcohol. The dieter then has to switch back to the previous diet to get rid of the bad smells.

Another enemy of healthy eating is your own psychology. When the petty tyrants all around you create stress with their nagging, controls, and imposed costs, it can get quite stressful, and many turn to soothing foods and the tonic of television. Just as one recovers, bam! you get another stress attack and go off diet to recover. Finally, after relentless stress attacks, you give in.

The mainstream culture is also opposed to healthy eating. After overcoming the body’s reaction to a diet switch, the food warrior faces fierce social opposition. Restaurants and cafeterias are geared to the standard high-fat salty and sugary diet. Healthy eating is especially difficult if one usually eats in the company or school cafeteria. They serve white rice rather than brown whole-grain. The pasta is seldom whole-grain, and even when they offer “wheat” bread, it is not whole grain.

One can eat a salad instead of the main dish, but then one sees others enjoying cooked foods that are denied to the healthy eater. The salads offered at almost all restaurants seldom offer organically grown fruits and vegetables. Then they have pots of fatty salad dressings that tempt the diet warrior.

Another enemy of healthy eating is conflicting advice. Some doctors and nutritionists advise low-fat diets, organically-grown foods, and supplements to ensure adequate amounts of vitamins and minerals. Other experts claim that most organically grown foods are not healthier, as the conventionally grown foods contain little pesticide, hormones, and toxic chemicals. Experts will prescribe various different supplements, and some say a healthy diet is sufficient, without supplements. Some experts say that some fats such as from olive oil are good for you.

Most nutrition experts agree that sugar is bad for health. The usual advice is to instead use stevia or xylitol. But almost all sweetened foods and drinks contain sugar or equivalents such as corn syrup, or sugar substitutes such as aspartame. Again, experts contradict one another, as some say that aspartame has been found to be safe, and other say that there are findings that indicate that aspartame is harmful in the long run. There is general agreement that xylitol is safe and healthy both for your metabolism and your teeth, yet few foods use it.

Some nutritionists say that optimal nutrition depends on one’s body type and metabolism. One problem in determining which expert is best is that often, the experts also sell products, so they have a financial interest in their advice beyond what is paid for the information. The ideal nutritional expert could be one who accepts payment for information, but does not sell or profit from the purchase of any supplement or food. However, if they determine that particular supplements are best, but are not sold conventionally, so they produce their own, maybe that is best.

The conflicting advice from medical and nutritional experts makes economics look good by comparison. Most economists at least agree on the law of demand, that higher prices result in lower quantities bought, and that trade is usually mutually beneficial. But the simple question of whether I should take a vitamin C supplement will not find agreement by nutritionists. Some say to get vitamins from foods, not supplements. Others say take the pills, but they disagree on whether natural or synthetic vitamins have the same effects, and there is a big variety of vitamins, so how does one know which is best?

All nutritionists at least agree on what is bad: white flour breads and pastas, excessive sugar, too much salt, trans hydrogenated fats. Just as in economics, there is a deadweight loss from taxation that reduces output and growth, in nutrition, there is a deadweight loss from eating junk food that makes you gain weight and will leave you dead sooner.

But even following this basic diet regime is difficult, as your body, your friends and family, and the conformist culture will all conspire to seek to defeat your healthy diet. One has to be a diet warrior to persevere in the face of such fierce opposition to healthy eating. Few have the stamina and motivation to persevere and do battle with the enemies of healthy eating, so they succumb. And that’s why people get fat.