If your body isn't keeping up like it used to, it might be time to overhaul your metabolism. Here's how to do it.
Break up the day.
Long, sedentary periods at the desk or watching TV put muscle, and metabolism, to sleep. Research has shown that taking brief breaks for light activity, like a 10-minute walk, can meaningfully speed up the rate the body burns glucose, lowering blood sugar levels.
Embrace the cold.
Wear a light jacket when you'd normally put on a coat, lower your thermostat a few degrees, and exercise in less clothing than you think you need. Being slightly cold has been proved to increase metabolic rate.
Mildly stressing your system by eating extremely lightly a couple of days a week makes muscle cells more responsive to insulin and more metabolically efficient. A popular way to do this is the intermittent "5:2 fast": Five days a week, eat normally; the other days, restrict your intake to 500 calories. If that sounds too daunting, you can glean similar benefits by eating an early dinner (say, at 7 pm) and a late breakfast (10 am), so that you go 14 or more hours without taking in calories — including milk in your coffee — each day.
Spicy dishes, especially those with capsaicin-loaded chilies, are proved to increase satiety briefly and raise metabolic rate by an average of 8 percent. (That may seem small, but who wouldn't take the boost?) Dense protein- and fiber-rich foods like nuts do the same thing by requiring more energy to digest.
Do hybrid workouts.
You'll raise your heart rate and strengthen muscles with this 40-minute burner, based on a routine created by muscle researcher Marcas Bamman: Choose five strength exercises that work major muscle groups — such as weighted squats, lunges, dead lifts, rows, and bench presses — and do three sets of eight to 12 reps. Instead of resting between sets, do 60 seconds of any body weight exercise (jumping jacks, burpees, mountain climbers, push-ups, or pull-ups). The idea is to move continuously, without any long breaks.
Use it or lose it.
Muscle burns sugar for fuel, and the more muscle you have, the faster your metabolism runs. Without strength training, however, muscle fibers (the tiny cylindrical cords above) begin to wither and then disappear for good. You can still get stronger using the fibers you have left — but you'll never be as strong as you could have been if you'd been strength training all along.