Of vice and men

Why It's Bad For You

According to Janis Jibrin, a nutritionist in Washington, D.C., pizza, lasagna, and fries raise insulin and blood-sugar levels, which can lead to weight gain.

How Much Is Too Much

If what Jibrin calls a "diabolical mixture of fat, salt and carbs" makes up at least one meal a day, or even several times a week, it's time to act.

Smart Substitute

Sweet-potato fries have more fiber and vitamin C; veggies and whole-wheat crust make a healthier pizza; quinoa is low-cal and high-protein.

How to Quit It

If you stop eating them, you stop wanting them. Replace white carbs with brown rice, whole grains, and quinoa, and limit portion size to 1 cup.

Why It's Bad For You

Sleeping isn't a major calorie burner, plus late-night munching throws off the eating-fasting schedule that prepares you to process food efficiently.

How Much Is Too Much

The occasional midnight snack is okay—if you have genuine hunger pangs—but a satisfying dinner should always see you through until morning.

Smart Substitute

If you actually are hungry and not hitting KFC out of habit, try a small 150-to-300-calorie combo, such as an apple with peanut butter.

How to Quit It

"Try the 12-hour rule," says Lauren Slayton, R.D., of Foodtrainers in New York City. "If you stop eating at 9 p.m., then wait until 9 a.m. to eat again."

Why It's Bad For You

Artificial sweeteners may raise insulin levels, which can increase appetite and fat storage, Jibrin says. Hence the research that links diet sodas to obesity.

How Much Is Too Much

"If you care about bones, teeth, and kidneys, you can't be on regular terms with it," Slayton says. For regular, read two or more times a day.

Smart Substitute

Naturally flavored sparkling water will give you the fizz factor, and iced tea (1 teaspoon sugar per cup) will ward off caffeine withdrawal.

How to Quit It

Drop your intake down to one can per day for three weeks; for the fourth week, have two cans, max; then cut it out altogether.

Why It's Bad For You

The stress reliever stimulates dopamine, which could lead to addiction, and then you risk skin irritation, premature ejaculation, and penile fractures.

How Much Is Too Much

If you use it in place of sex, or if it interferes with work, sleep, or socializing, cut back, says Jeffrey Morrison, M.D., of the Morrison Center in New York City.

Smart Substitute

The obvious upgrade: According to a U.K. study, sex with a partner is 400 percent more satisfying than going it alone.

How to Quit It

If you're stressed or bored, break a sweat—exercise releases endorphins, and studies show men who work out have better sex.

Why It's Bad For You

Excess can cause anxiety, insomnia, and stomach issues. Plus, you constantly need more to feed the high, which erodes natural energy and memory levels.

How Much Is Too Much

"You shouldn't drink more than two 8-ounce cups a day," Slayton says.

Smart Substitute

Sip green or oolong tea; when you do have your daily joe, add almond milk and stevia in lieu of calorie-laden condiments at the coffee shop.

How to Quit It

There's no need to go cold turkey, but if you want to ease up, keep it for a specific use—have a small cup before an early workout or a big morning meeting.

Why It's Bad For You

UV radiation is a carcinogen—you're inviting fine lines, wrinkles, and rough skin.

How Much Is Too Much

Hitting a tanning salon before age 35 raises your chance of developing melanoma by 75 percent; the risk increases the more times you go.

Smart Substitute

Use a gradual self-tanning face cream such as Anthony Logistics Self Tanner with Anti-Aging Complex ($30).

How to Quit It

Get your fix from the sun, but apply daily a UVA-and-UVB-blocking sunscreen that has free-radical-fighting antioxidants to shield skin from those rays.

Why It's Bad For You

Processed stuff like Twizzlers spike dopamine so you need more to feed the craving. "That's why you get addicted to Skittles, not nectarines," Jibrin says.

How Much Is Too Much

If you're scarfing down a bag of peanut M&Ms or a Hershey's bar every afternoon—stop. Instead, break off a few squares (of the dark variety).

Smart Substitute

Dark chocolate has about half the amount of sugar as milk chocolate, and you get more of the heart-helping flavonoids. But scrap the fattening fillers.

How to Quit It

Swap in fruit when that 3 p.m. craving strikes. "Once you get away from ultra-sweets, your taste buds will appreciate the lower dose," Jibrin says.