Good nutrition means knowing your nutrients. Your body needs a variety of nutrients to remain healthy. In fact, there are six categories of nutrients which our bodies need each day:

Carbohydrate
Provides 4 calories per gram. Energy; preferred fuel for most body functions.
Primary fuel during high-intensity exercise.

40 to 55 percent of total calories for bodybuilders or those trying to get lean.
50-60 percent for sedentary people.
55-65 percent for endurance athletes.

Protein
Provides 4 calories per gram. Growth and maintenance of body tissue; building of enzymes, hormones and antibodies; maintaining fluid and electrolyte balance and acid-base balance.

0.5 gram/pound of body weight if sedentary.
0.6 grams to 0.8 grams per pound for endurance and strength athletes.
1.0 to 1.2 grams per pound for bodybuilders (30% to 40% of total calories).

Fat
Provides 9 calories per gram. Energy; maintenance of body temperature; protection of organs; to make hormones; provide essential fatty acids; carry fat-soluble vitamins (A, D, E, and K). 10 to 25 percent of total calories, depending on fitness goals and bodytype.

Water
Water reduces fat deposits in the body, flushes out waste and toxins, helps maintain muscle tone, moisturizes skin, and may even suppress appetite. It also carries nutrients, provides joint lubrication and shock absorption, and helps in regulating body temperature. 8 to 12 cups/day, more when exercising. Drinking water, fruit and veggie juices, milk, soup, non-caffeinated and non-alcoholic beverages.

IMPORTANT: Many people would lose weight if they did nothing but stop drinking. Alcohol is the only form of calorie your muscles cannot burn for fuel, it slows your metabolism, and also stimulates your appetite for fatty foods.

The reason alcoholic beverages are high in calories is due to the alcohol, which contains 7 calories per gram. Although carbohydrates are found in alcoholic beverages (usually 5-12 grams), there are no carbohydrates in the alcohol itself, as they are two different molecules.

Eating for a variety of reasons

"The first wealth is health."
~ Emerson

Heart disease and cancer are two of the leading causes of death in the world. Evidence suggests that some of the root causes of these illnesses are related to overeating and insufficient nutritional intake.
Eating when our bodies don't really require food can easily lead to overeating. And overeating can lead to health related problems. We eat for a variety of reasons:

Despite this awareness, the consumption of refined processed and junk food continues to be the main staple for many people, which in effect, starves the body of its required nutritional needs. Busy and hectic lifestyles make it too easy to turn to processed or junk food as quick and easy options.

Eating Junk Food
Some characteristics which may cause certain foods to be considered "junk food" are high content of refined sugar, white flour, trans fat and saturated fat, salt, and various additives such as preservatives and coloring agents. Other characteristics include deficiency of proteins, vitamins, fiber and other nutrients required for a healthy diet.

Eating junk food and drinking sodas have been linked to causing or the worsening of health conditions such as: high blood pressure, heart disease, cancer, arthritis, obesity and diabetes.
The following contemporary illnesses may all be prevented by eliminating junk food and soda drinks from your diet:

In the process of being digested, junk food robs your body of valuable nutrients ... junk food and refined sugar also inhibit your liver's production of enzymes needed in the detoxification process.