How life used to be, 10,000 years ago:

• When humans were hunters and gatherers, we expended about the same amount of calories we took in.
• We learned to eat until we were full, because we didn't know when food would be available again.
• We ate lean meat and fresh fruits and vegetables that were low in calories.
• Our bodies retained fat so we could survive when food was scarce.

Modern conveniences such as cars and elevators have reduced the amount of exercise we get each day. As a result, our energy balance—calories in vs. calories out—is out of kilter.

Nutritional pollution

High-calorie foods are inexpensive and plentiful—over 90% of what Americans are eating is processed. When we speak of "nutritional pollution," we're referring to foods that are too high in:

• sugar, especially high fructose corn syrup
• fat
• salt
• unnecessary artificial ingredients

Examples of the habits of disease:

• Eating only three (or fewer) times a day
• Having only coffee or orange juice for breakfast
• Watching TV after 10:00 p.m. regularly
• Eating more pasta and rice
• Eating out at least four times a week
• Getting four hours of sleep
• Eating dessert
• Drinking more caffeinated drinks than water
• Drinking more diet soda than water
• Wearing clothes with elastic waistbands

Examples of healthy weight-maintaining habits:

• Eating a substantial breakfast each morning
• Using the stairs whenever possible
• Parking far away from the store and walking
• Taking a five-minute power nap when tired
• Exercising five to seven days a week
• Getting seven to eight hours of sleep each night
• Eating fish at least twice a week
• Eating more fruits and vegetables
• Drinking at least eight glasses of water per day
• Choosing healthy-minded friends