Most weight loss programs begin with a reducing diet (designed to promote weight loss) which creates its effect by limiting how much of different types of foods one can eat. There are a bewildering number of reducing diet styles, however. Some recommend a simple reduction in the total amount of food consumed, while others recommend specific reductions of particular types of foods consumed (breads and pastas, for instance). A knowledge of basic nutrition concepts helps us to understand why the variety of recommendations exist.
The Food Pyramid
A good starting place for diet and nutrition information is the USDA's research-based Food Pyramid guide for selecting a healthy diet.
The food pyramid starts by dividing foods into the following six food groups:
- Meat & Beans
The six groups are then arranged into a pyramid shape to indicate the relative proportions of each food that people should eat each day. For example, the Grains (bread, cereals, rice and pasta) group takes up a larger percentage of the pyramid's area than other groups to indicate that proportionally more servings of bread, cereals, rice and pasta are appropriate to eat each day versus other groups. Importantly, not just any grain is recommended. At least half of the grains eaten in a given day should be 'whole' grains, which contain the grain germ (fertile seed part), and the bran (hard outer seed coating). Look for whole wheat breads and pastas when making food choices, if possible.
The Fruits and Vegetables groups's area is smaller than the Grains group, but larger than the Milk and Meat & Beans groups, suggesting that more fruits and vegetables are to be consumed than milk, meat or beans for balanced nutrition. The types of fruit and vegetable choices made are important as well. Whole, fresh fruit is much better for you than fruit juice. Dark green and orange vegetables such as spinach and carrots are in general better for you than vegetables that do not have these colors, and fresh vegetables are in general better for you than canned vegetables. When choosing dairy or meats to eat, the pyramid suggests that you choose lower fat varieties. When chosing oils and fats to use for cooking and eating, the pyramid indicates that liquid choices (such as olive oil) are better than solid choices (such as butter, margerine, or shortening). The Oils group is the smallest of all the groups, indicating that as a percentage of your total diet, relatively few oils should be consumed.
For the first time ever, the pyramid now includes a physical exercise component as part of the essential food groups, to indicate that regular physical exercise for at least 30 minutes a day, most days of the week (60 minutes a day for children and teens!), is vital for everyone's health.
Carbs, Fats and Protein
The six food groups recognized in the food pyramid may be each very different in origin, composition and taste, but they all contain nutrients necessary for building and maintaining bodily health. There are six classes of necessary nutrients found in foods: carbohydrates, fats, protein, vitamins, minerals and water. Working together, these nutrients perform three vital life functions: they provide energy, they promote body growth and maintenance, and they assist in regulating bodily processes. Carbohydrates, fats and proteins work together to provide us with energy. Proteins, fats, vitamins, minerals and water promote growth and maintainance and are necessary for appropriate body process regulation. All six nutrient classes must be present in sufficient amounts at all times or the body will not function properly.
Different nutrient classes contain different amounts of calories. For instance, carbohydrates and proteins provide only 4 calories per gram while fat provides 9 calories per gram. This is why high fat foods are more 'fattening' than lower fat foods; they are more calorically dense.
With the exception of water, each nutrient class contains a variety of different subtypes of that nutrient. Some of these nutrient subtypes can be better for health than others. For example, within the fats class, there are saturated fats, mono-unsaturated fats and poly-unsaturated fats. Eating a diet high in saturated fats (such as are found in butter, lard, and shortening) is known to increase LDL (bad) cholesterol levels and increase the risk for cardiovascular disease. Trans-fatty acids (man-made saturated fats produced via a process called hydrogenation), found in most margarines and store-bought baked goods, are now thought to pose similar health risks. On the other hand, mono-unsaturated and poly-unsaturated fats (such as occur in olive oil) help to lower LDL cholesterol.
Like fats, carbohydrate subtypes are not all equally nutritious. Foods rich in refined sugar and flour (white bread, cakes, cookies, etc.) provide 'empty' calories as they are mostly devoid of nutritional value. In contrast, complex unrefined carbohydrates such as those found in whole grain products (brown rice, bran, whole wheat bread, etc.) and fruits and vegetables provide essential nutrients as well as fiber in addition to providing energy. Fiber comes in two helpful varieties. Insoluble fibers helps to keep the digestive and eliminatory tract functioning regularly, while soluble fiber helps to keep the arteries clean by reducing LDL cholesterol in the bloodstream.
All nutrients, including carbohydrates, fats and proteins, are essential for life and should be present in a healthy diet. Since all classes of nutrients are necessary the wisdom of severely limiting or eliminating any category is questionable. Rather than attempting to eliminate nutrient classes as some reducing diets seem to suggest, the wisest course is to select a diet based heavily on the healthier types of nutrients from each nutrient class. Such a diet includes fresh fruits and vegetables, whole grain breads and cereals, lean meats, fish and poultry, low fat or nonfat dairy products, and the sparing use of healthy fats such as olive oil. Refined sugars, white flour, and partially-hydrogenated oils should be avoided. Less nutritious (but still delicious) foods, including steaks, hot dogs and sausages, cream and butter, and cake and ice cream can be eaten on an occasional basis but should not become staples of an everyday diet.