A calorie-restricted diet can extend the lives of organisms from yeast to fruit flies to rodents, as well as improving their health and preventing disease. But just because cutting calories helps animals with short lifespans doesn’t mean that humans will reap similar benefits. So the 2009 discovery that calorie-restricted diets also increase the longevity of already-longer-lived rhesus monkeys was exciting news.
But don’t pull out a calorie calculator quite yet. The latest word on the subject, from a new paper in Nature, suggests that the 2009 study might not tell the whole story: this team found that caloric restriction doesn’t actually grant rhesus monkeys longer lives.
So. Tired. From reading email.
A day of hard mental labor—writing emails, taking the SAT, competing in the national crossword competition—can leave you beat. But how, exactly, is that possible? You haven’t done any heavy lifting, at least not with your muscles.
Ferris Jabr at Scientific American MIND takes a crack at investigating this phenomenon, exploring the science on whether thinking really hard burns calories, or whether the exhaustion is coming from something else. He writes:
Although the average adult human brain weighs about 1.4 kilograms, only 2 percent of total body weight, it demands 20 percent of our resting metabolic rate (RMR)—the total amount of energy our bodies expend in one very lazy day of no activity.RMR varies from person to person depending on age, gender, size and health. If we assume an average resting metabolic rate of 1,300 calories, then the brain consumes 260 of those calories just to keep things in order. That’s 10.8 calories every hour or 0.18 calories each minute. (For comparison’s sake, see Harvard’s table of calories burned during different activities). With a little math, we can convert that number into a measure of power.
When we rip open a 100-calorie snack pack, few of us have an idea of how much energy that really is–or how much walking, biking, or schlepping groceries it will take to burn it off. But what if nutrition labels included descriptions of how much exercise you’d need to burn off that candy bar?
One recent study explored that possibility by testing the effects of signs describing in one of three different ways the energy contained in a sugary drink. Researchers found that a sign that said “Did you know that working off a bottle of soda or fruit juice takes about 50 minutes of running?” halved the number of drinks purchased from a drink cooler by African American teenagers, while signs that mentioned calorie count or percentage of total recommended calorie intake did not have a significant effect. Though the study was pretty small, and thus should be verified with larger studies, the effect seems plausible, given that exercise is a much more concrete measure of energy value than calories. Some health campaigns have in fact already taken up this tactic: if you’re a New Yorker, you may have noticed subway ads using exactly this strategy, linking the calories in a 20-oz soda with the three-mile walk between Yankee Stadium and Central Park. Read More