Yes, the diet is by definition restrictive (thought practitioners simply call it CR).
Men consume 1,800 calories, rather than the recommended 2,500; women eat only 1,500 to 1,700 calories per day, compared with the recommended national average of 2,000. But that doesn't mean they don't eat well.
On a recent morning, Cavanaugh, who lives in coastal North Carolina, prepared his breakfast, the same one he has had most days since starting the calorie-restrictive diet eight years ago: a quarter cup each of oatmeal, oat bran, powdered skim milk, and liquid skim milk. After two minutes in the microwave, he topped the concoction with half a cup of frozen blueberries—to provide antioxidants and improve mental crispness—and two tablespoons of sunflower seeds that will fulfill 60 percent of his daily vitamin E requirements. He washes down his 451-calorie breakfast with a cup of coffee. He won't eat again until dinner and claims he won't be hungry until then.
"My breakfast gives me more than half my nutrition for the day," says Cavanaugh, who's pre–calorie restrictive eating habits included bacon and eggs, hot dogs, chips, and cinnamon buns. "It's so filling, I just don't get hungry for lunch."
A retired Marine who stands 5 feet 10 inches tall, Cavanaugh eats has seen positive physical results since he scaled back his calorie intake. Prior to embarking on the diet, he weighed 178 pounds, had a body mass index of 26 (an ideal BMI falls between 18.5 and 24.9), and his cholesterol level was 273 (the ideal is less than 200).
Five months into his new lifestyle, Cavanaugh's cholesterol dropped 103 points, and his triglycerides dropped from 145 to 63 (a healthy number is 150 or below). Now 140 pounds, he claims he hasn't had a cold in eight years, and the chronic athlete's foot and jungle rot he suffered since his time in the Marines has disappeared completely. His energy levels have skyrocketed. "Remember when you were a kid and you would suddenly just take off running across the yard because of the exhilaration of energy? That exhilaration came back to me," Cavanaugh says. "I haven't felt like this since I was a teenager playing tackle football."source