Step 3: Exercise Smarter
To hit old age with max strength and vigor, you want to keep on healthy muscle and keep off useless fat. The best prescription for that, according to studies by Church and others, is twofold: You need cardio to protect the heart and lungs and to build mitochondria in the muscle cells, which helps them generate more power over time. Most cardio won't, however, raise your metabolic rate after you're done exercising. Resistance training will.
It creates a kind of perma-burn by building muscle that always consumes sugar, whether you're exercising or sitting on your couch.
Because few of us have the time or energy to do cardio one day and weights the next, trainers and exercise physiologists are increasingly designing "one-stop shopping" workouts. These routines focus on moving quickly through compound strength exercises that target the biggest muscle groups — lats, glutes, quads, and hamstrings among them, which suck up the most sugar for fuel — and simultaneously elevate the heart rate and tax the lungs. Bamman, for one, has seen good results pushing his subjects through a weightlifting workout that requires them to do fast-paced body weight exercises between traditional lifts.
What all this adds up to is a paradigm shift in how we think of metabolism. Skinny guys aren't bulletproof, but with the right lifestyle, none of us has to experience a dramatic metabolic drop. "Our studies show that excess body weight and physical inactivity are the major causes," says Bret Goodpaster, a metabolism expert at the Sanford Burnham Prebys Discovery Institute in Lake Nona, Florida. "Aging doesn't have much to do with it."