Poor nutrition may be one of the easiest conditions to self-diagnose. Look at the food pyramid and the suggested servings. Look at your diet. Are you getting the recommended daily amounts of fruits and vegetables? Enough calcium? Read the labels and compare what you eat to what you need. You may discover that even if your weight is ideal, you are not getting enough nutrition.
There are thousands of dietary supplements on the market, including 40+ essential nutrients alone and in various combinations, i.e. vitamins, minerals, trace elements and fatty acids. However, a number of other nutrients are "conditionally essential", meaning that the body normally can make these molecules, but some people do not make optimal amounts. Examples are L-carnitine, alpha-lipoic acid, the methyl donor betaine,  chondroitin sulfate, coenzyme Q10, choline, amino acids such as tyrosine or arginine, and "essential" sugars normally formed in the body. 
Grains, vegetables and fruits are essential to getting the vitamins, minerals, complex carbohydrates (starch and dietary fiber) and other nutrients you need to sustain good health. Some of these nutrients may even reduce your risk of certain kinds of cancer. But experts say we rarely eat enough of these foods. To make matters worse, we also eat too much of unhealthy types of food, including fat (and cholesterol), sugar and salt.
Once you slice and sauté your way to a fabulous feast, you don't have to finish every bite. "We're conditioned to think that if we don't devour everything on our plate, we are misbehaving," McKenna says. But if you keep munching even after you're full, you are using your body as a storage unit. If there's enough left over for lunch tomorrow, pack it up and put it in the fridge. Otherwise, toss scraps in the trash. We promise we won't tell your mom.
Much of the sugar we eat is added to other foods, such as regular soft drinks, fruit drinks, puddings, ice cream and baked goods, to name just a few. Soft drinks and other sugary beverages are the No. 1 offenders in American diets. A 12-ounce can of regular soda contains 8 teaspoons of sugar, exceeding the daily maximum amount recommended for women.
The use of dietary supplements is widespread. High doses of vitamins are thought to be helpful because they help the body recover from damage and maintain itself long-term. Many vitamins are not harmful in doses even 10 to 100-fold higher than officially recommended. Some governments warn about possible negative side effects, even including increased mortality from "excessive" intake of certain supplements. However, supplements of essential nutrients have been available for more than 80 years. They are known to be safe, and the observed side effects are generally mild with few exceptions.
Minerals are the exogenous chemical elements indispensable for life. Four minerals: carbon, hydrogen, oxygen, and nitrogen, are essential for life but are so ubiquitous in food and drink that these are not considered nutrients and there are no recommended intakes for these as minerals. The need for nitrogen is addressed by requirements set for protein, which is composed of nitrogen-containing amino acids. Sulfur is essential, but for humans, not identified as having a recommended intake per se. Instead, recommended intakes are identified for the sulfur-containing amino acids methionine and cysteine. There are dietary supplements which provide sulfur, such as taurine and methylsulfonylmethane.
What is moderation? In essence, it means eating only as much food as your body needs. You should feel satisfied at the end of a meal, but not stuffed. For many of us, moderation means eating less than we do now. But it doesn’t mean eliminating the foods you love. Eating bacon for breakfast once a week, for example, could be considered moderation if you follow it with a healthy lunch and dinner—but not if you follow it with a box of donuts and a sausage pizza.
Substances which the FDA regulates as food are subdivided into various categories, including foods, food additives, added substances (man-made substances which are not intentionally introduced into food, but nevertheless end up in it), and dietary supplements. The specific standards which the FDA exercises differ from one category to the next. Furthermore, the FDA has been granted a variety of means by which it can address violations of the standards for a given category of substances.