Type 2 diabetes (the kind associated with being overweight) increases the risk of Alzheimer's, probably by increasing inflammation or arterial aging, but also because too much of the hormone insulin in the brain can stimulate beta-amyloid buildup. In fact, Alzheimer's is now being called type 3 diabetes.

When you're over 65, HDL is more important than LDL. Although statin drugs can be life saving, the net effect is that some choices may reduce healthy HDL cholesterol too. So you may want to try an alternative, like taking niacin, vitamin B5, and omega-3 fatty acids, and exercise for lowering your LDL while keeping your HDL high.

Some people may say there's no harm in taking antibiotics if you feel bad, but if you're fighting off a viral infection like the flu, antibiotics can hurt you more than they can help. That's because the overuse of antibiotics can cause collateral damage. You'll kill off all the bacterial allies in your gut and leave the evil virus untouched. If you do have to take antibiotics for a bacterial infection, protect your gut by eating probiotics, simple foods low down on the food chain that bacteria love and that can help reduce inflammation.

If you don't smoke but live or work in a smoke-filled environment, that's still going to age you. Spending just one hour in the presence of secondhand smoke is the equivalent of your smoking four cigarettes. Whether the smoke you're breathing is from your own cigarette or someone else's, it ages your arteries, increases your risk of heart and lung disease, weakens your immune system, and promotes cancer.

Did you think that just because diet soda was calorie-free that it was guilt-free, too? Sorry. Even drinking diet drinks is associated with a higher risk of metabolic syndrome. Consumption of sugar (or its equivalents, like corn syrup) in soft drinks has been linked to obesity in children and adolescents. But a recent study of almost all 50-year-old men and women in Framingham, Massachusetts, found that having more than one soft drink, whether sugared or diet, increased the risk of metabolic syndrome by 44 percent over a four-year period. The risk was increased similarly whether the drink was sugared or diet. One theory is that the high sweetness of drinks conditions people to crave sweet foods; another is that ingredients in the drinks can lead to insulin resistance or inflammation.

Stop kidding yourself. Research suggests that obese adults with diabetes often say they eat less than they actually do—a problem that can make it hard to manage the disease. On average, diabetic adults reported a calorie intake that was nearly one-quarter lower than they would need even for their most basic bodily functions. Many obese people have inherited abnormalities in the complex pathways that help signal them that they are satiated: They lack the cues to stop eating when they're full. It can help to take small portions and/or to eat only half of what's being served to try to work around this problem with satiety signals. Reducing your food intake a little bit every day (100 calories), which can be done without the insatiable hunger that usually sabotages most diets, will help reduce weight gain and promote weight loss.

You think secondhand smoke is bad? Think about secondhand sleep. Spouses lose an average of one hour a night of sleep because of their partners' snoring (not continuous, but a cumulative effect of a minute here and there). If you're suffering, earphones playing white noise or meditation-type music can help. So can separate bedrooms.

The number of sexual partners you have may increase your risk of prostate cancer because it increases your potential exposure to infections. The number of ejaculations you have, however, does not. Prostate cancer is at the stage where cervical cancer was some 20 years ago. We knew then that cervical cancer was correlated with the number of sexual partners a women had, and now we know it is caused by a virus (and can be reduced substantially by a vaccine). We may eventually discover that there's a virus associated with prostate cancer as well. Conversely (and to boost survival of the species, we think), mutually monogamous sex three times a week is reported to be associated with a 50 percent reduced risk of prostate cancer.

Continual burning of your esophagus is just like the continual burning of your skin; it causes cellular damage and substantially increases the risk of cancer. As you get heavier, the angle between the esophagus and the stomach (normally, the esophagus enters a side door) straightens out, and acid can easily shoot up into your esophagus. While you're losing weight (which will restore the normal angle), take a course of medications like over-the-counter Prilosec, Zantac, or Pepcid to help heal the injured tissue.

Chronic exposure to noise loud enough to make you raise your voice can increase heart attack rates by 50 percent, especially if this is true at both work and home. And if you work in a noisy place, it's that much more important to make sure you live in a quiet one. So pick an apartment on a higher floor or in a suburban area, or petition for a quieter work environment.

Know your biggest aging enemies—the major agers.