UCSF study takes closer look at calorie restrictors
Published 4:00 am, Thursday, April 28, 2011
Trent Arsenault has eaten the same breakfast, lunch and dinner almost every day for the past four or five years: a fruit smoothie in the morning, a spinach salad at noon and another fruit smoothie after work.
Every now and then he'll add a snack to his day. Maybe a spoonful of almond butter or a few walnuts.
All in all, Arsenault consumes about 1,800 calories a day - or several hundred calories fewer than what a typical man his size would expect to eat.
But Arsenault is hardly typical. At 6 feet 1 inch tall, he weighs just 150 pounds, and he purposely restricts the calories he takes in because he believes a strict diet will allow him a much longer, healthier life than his peers.
"My blood pressure is equivalent to a 10-year-old's. My triglyceride level is very healthy for a 20-year-old," said Arsenault, a 35-year-old engineer who works out of his home in Fremont. "It took years for me to refine my diet to what works for me and keeps me healthy. But I think it's worth it. I haven't gotten sick once since being on this diet."
Arsenault is a calorie restrictor - someone who regularly consumes roughly a third fewer calories than an average person his or her size would eat, while still meeting all basic nutritional needs. Unlike anorexics or others with eating disorders, calorie restrictors don't usually care about weight loss or body image. They want to live longer.
And they may be on to something, based on several scientific studies of calorie restriction in animals and a handful in humans. In a major, decades-long study of rhesus monkeys that ended in 2009, scientists found that animals kept on a diet with 30 percent fewer calories than a control group had fewer cases of diabetes, cancer and heart disease.
The diet study
Now researchers at UCSF are looking at a group of 28 people - including Arsenault - who strictly control their calorie intake. Specifically, the scientists are studying what effect the diets may have on certain markers that suggest someone may live a long life, such as cholesterol and blood pressure levels and the length of an individual's telomeres, which are the caps on the ends of chromosomes that regulate cell aging.
They'll also be looking at several molecular-level signs of aging that have never been studied in humans before.
"This study will be our glimpse into their future, even though we won't be following them their whole lives," said Elissa Epel, an associate professor of psychiatry at UCSF who studies the relationship between stress, food and cell aging. "We're looking at the cellular markers that these people believe they are manipulating through their diet."
Scientists aren't sure why calorie restriction might help people live longer, but it's been studied for decades as a potential pathway to the always-elusive fountain of youth. One theory is that starvation puts cells into some kind of preservation mode, focusing more energy on maintenance.
But dieting is stressful, and stress hormones like cortisol are well known to be damaging to the body. Epel wonders what is happening in the bodies of calorie restrictors that lets them remain healthy even as their body is flooded with cortisol - or if, perhaps, they're not quite as healthy as the dieters and doctors assume.
A healthy skeptic
Janet Tomiyama, the researcher who is leading the UCSF study, said she's long been a diet skeptic - she knows that while most calorie-restricting diets are successful in the short term, the results rarely last more than a year or two.
"But every time I would say dieting isn't necessarily healthy, people would then say calorie restriction is the only intervention we know of that increases life spans," Tomiyama said.
"I don't know that they're living longer, and I don't know that they're healthier," she said. "I'm a scientist, so I'll wait for the empirical evidence before I change my behavior."
Aside from looking for evidence that the calorie restrictors are healthier than their normal- or over-eating peers, Tomiyama is also investigating what makes extreme dieters tick - how they're able to severely limit their food intake while living in a society where more than half the population is overweight and where unhealthful foods are ubiquitous.
That's the science that fascinates some weight-loss experts. They can't imagine most Americans sticking with a severe calorie-restriction diet for years on end, but people who manage it might offer some secrets for long-term weight maintenance.
Not for everyone
The UCSF study probably won't yield insights on dieting behavior that can be applied to everyone - for starters, almost all of the participants are highly educated men, and what works for them may not work for most other people. But it's a good start, said Dr. Wayne Smith, co-director of Kaiser San Jose's medical weight management program.
"A lot of people diet successfully for a limited time, but to maintain that for a long time, that's hard," Smith said. People are surrounded by "drivers" that compel them to eat, he added, and it's hard to fight those urges. "It will be interesting to see what the triggers for eating are in this population (of calorie restrictors), or maybe if they have a trigger not to eat."
No one - not even Arsenault - suggests that calorie restricting is for everyone. It's not a lot of fun, and it's downright impractical for most people. And certainly without more evidence of the long-life benefits in humans, few scientists are willing to guarantee that a very low-calorie diet will add years to a life span.
But Arsenault, for one, is happy to be the guinea pig in this case. He started calorie restricting 10 years ago, after realizing his "computer hacker" diet of Pringles and sodas and Pop-Tarts was setting him up for a lifetime of health problems. Now he feels great, and he enjoys his variety-free diet. Even if he does miss Girl Scout cookies sometimes.
"I'm a fan of the peanut butter ones," he said. "But we can give that up. There are other foods that are just as good. The smoothies I make are better than anything I could get in Alice Waters' kitchen."
UCSF researchers are recruiting normal eaters to participate in their study on aging and calorie restriction. Participants should be highly educated men who are average weight or overweight. To apply, send an e-mail to firstname.lastname@example.org.