Jeffrey Peipert wasn’t necessarily after any potential anti-aging benefits when he enrolled in the Calerie trial. And he wasn’t purely aiming to advance the research on cellular aging. He mostly wanted to lose weight.
Peipert was 48, stood at 5 feet, 5 inches, and weighed 174 pounds. During the trial, he cut his daily food intake from 3,300 to 2,475 calories, and his weight dropped to 147 pounds. His health biomarkers, especially his blood pressure, were excellent. “It was a remarkable drop in blood pressure. That taught me that, for our health, if we were just a little thinner, we’d be better off,” says Peipert, a gynecologist and researcher at the Indiana University School of Medicine.
The big takeaway from Calerie, Longo says, is that the biomarkers of health are controllable through weight loss. “So if your doctor is telling you that you need drugs to control these things, that’s not true,” he says.
Not All Magic
Although CR might be metabolic magic, it’s no magic bullet. Some mice bred to carry certain genes for lab research don’t benefit from it, and it actually shortens life in other genetically modified mice. The deprivation can weaken the immune system of very young and very old animals, making them susceptible to disease. And although cutting calories by 25 percent has been standard, it’s not clear if that’s best for animals and humans.
As with mice, people react differently to food deprivation. In recent years, scientists have learned that genetics, diet composition (amount of carbs, protein and fats), regular exercise and other factors play a role in CR’s effectiveness.
Peipert’s experience in the Calerie trial points to these issues. Despite his banner biomarkers, he had trouble sleeping, a reduced libido, low energy and was hungry most of the time. “I used to love to garden,” says Peipert, now 57. But during the trial, “I was wheeling a wheelbarrow around full of dirt, and I felt weak. I wasn’t myself.”
These types of side effects weren’t more common in CR dieters overall, but several people had to pull out of the study because of safety concerns. Noted side effects of CR are chronic loss of bone density and lean body mass, and excessive weight loss. Some CR dieters have body mass indexes in the teens, which suggest malnutrition and frailty, Longo says.
CR can lead to psychological issues, too. These were minimal in the Calerie trial, but Ravussin says that’s likely because people were screened for predispositions: food fantasies, irritability and social isolation, he says. Some of the Biosphere 2 scientists said they became prickly and obsessed about food during their 21-month deprivation.
Kelly Vitousek, a psychologist at the University of Hawaii who has written review papers on CR, says these problems make sense from an evolutionary perspective; food is one of our top priorities. “Don’t waste your time on other stuff,” she says. “Think food, not about socializing, not about sex. Be preoccupied with food. Obtain it.”
During the Biosphere 2 experience and the Calerie trial, some researchers hoped CR would become a viable regimen. But the enthusiasm has significantly cooled. While side effects were an issue, people’s inability to stick to a significantly reduced calorie load every day was the hammer blow. At this point, fasting was CR’s heir apparent: It seems eating nothing on occasion might be better than eating less all the time.