Of all the depressing developments that come with age--ear hair, the cute assistant over in advertising calling you "sir"--a slower metabolism is high on the list. It's just one of those things: The older you get, the fewer calories you burn. A 180-pound man in his 40s burns, on average, about 12 fewer calories per hour at rest than a man of the same weight in his 20s. So we're talking a 288-calorie handicap before the day even begins.

But we're going to let you in on a little secret: It doesn't have to be that way. Several recent studies throw into serious doubt the notion that a slower metabolism is some fixed biological consequence of age, as opposed to a function of the bad habits people get into as they get older. That means it's also perfectly reversible. And, surprisingly, one of the biggest changes you can make to rev yours up is to eat more.

It all has to do with a concept physiologists refer to as "energy flux." When we talk about "revving," it's not just a figure of speech. The number of calories a person's body burns while just doing nothing is a direct product of the calories he takes in and moves out during meals and exercise. The more calories that enter and exit the system--in and out, in and out--the more the body's built-in calorie burner gets going and stays going, sort of like your standard pull-cord lawn mower engine. As it happens, younger people work out more and also eat more. Older people tend to slow down and eat less. (They still eat more than they should given their activity levels, but it's less than they used to in their teens and 20s.) As a result, older people end up turning their metabolisms into the nutrition equivalent of a weed- and mud-crusted mower that's been sitting in the back of the garage for years.

The plan below is designed to help you break out your magnificent piece of calorie-burning machinery again and get it working all summer long. You'll note that it calls for you to increase the intensity of your workouts and slightly tailor the content and timing of your meals. You'll also be happy to see that it has you eating a lot of tasty food. Sound good, sir?

Eat More, Weigh Less

BREAKFAST
Best choice: 2 cups of Kashi GoLean cereal with 2 cups of milk
Whole grains keep your weight down by filling you up, and protein requires your body to burn more calories to process it than any other food--a sure way to increase energy flux. Kashi and milk provide a huge variety of whole grains and 42 grams of protein. Plus, the calcium in the milk seems to work as a kind of metabolic mojo, helping people lose more weight than you'd think they would given their total number of calories.
Other choices: oatmeal; egg-and-cheese whole-grain burrito

LUNCH
Best choice: 16-oz bowl of chili
Animal protein not only cranks your metabolism, it also helps generate testosterone, which burns fat while building muscle. Besides the beef and fiber- and protein-rich beans, the other key metabolizing ingredient is the capsaicin in the red pepper.
Other choices: turkey on whole-grain; chicken; tuna wrap with low-fat mayo

Metabolism-Boostin' Chili
If you have time to cook your own, try this recipe from John Williams, coauthor of the ebook Gourmet Nutrition (johnberardi.com)

Ingredients
1 pound ground sirloin
3 cans (11 oz total) V-8 juice
1 can (15 oz) kidney beans, drained and rinsed
1 can (15 oz) crushed tomatoes
bag (8 oz) frozen mixed peppers (yellow, green, red)*
1 tbsp dried minced onion
1 tbsp paprika*
2 tbsp chile powder*
Cayenne pepper, to taste*
1 tbsp garlic powder
1 tsp ground cumin

*contains capsaicin

Directions
Brown the beef in a large nonstick skillet over medium-high heat, about 10 minutes. Drain the fat. Add the V-8 juice and bring to a boil over high heat, then add the remaining ingredients, one at a time, sturring until the mixture returns to a boil. Reduce heat to low, cover, and simmer for 10 minutes before serving.

Makes 3 2-cup servings, each with 404 calories, 43 grams of protein, and 11 grams of fiber.

SNACK
Best choice: 1/4 cup of cashews
That amount of nuts has about 4 grams of protein, but its main punch comes from monounsaturated fat, the same fat in olive oil. A noted 2003 British study found that eating more of it led to fat loss of six pounds in four weeks, with no other diet changes.
Other choices: peanut butter on apple or whole-grain bread; yogurt; cottage cheese