Natural “exercise” hormone transforms fat cells

Exercise makes cells burn extra energy—that’s one way it helps control weight. It also generates a newly discovered hormone, called irisin, that transforms energy-storing white fat cells into energy-burning brown fat cells. Irisin also appears to help prevent or overcome cellular changes that lead to type 2 diabetes.

“Irisin travels throughout the body in the blood and alters fat cells,” explains Dr. Anthony Komaroff, editor in chief of the Harvard Health Letter, in the June 2012 issue. “If your goal is to lose weight, you want to increase the number of brown fat cells and decrease white fat cells.”

Fat “color” makes a difference
White adipose tissue, more commonly known as body fat, is the tissue that dimples thighs, enlarges waists and derrieres, and pads internal organs. Each white fat cell stores a large droplet of fat. Brown fat, in comparison, is chock full of energy-burning mitochondria. Its main function is to generate body heat by burning fat.

Babies are born with brown fat, but it was thought to gradually disappear. In 2009, several studies showed that adults still have brown fat cells lurking in their bodies. Earlier this year, a team led by Dr. Bruce Spiegelman, professor of cell biology and medicine at Harvard Medical School, identified irisin in mice and humans. His team also showed how irisin transforms white fat cells into brown ones, at least in mice. The same thing is likely to happen in humans, too, but that remains to be worked out.

This transformation helps the body burn more energy during exercise. The effect lingers, since brown fat cells keep burning fat even after you’ve stopped exercising. In addition, Spiegelman’s work showed that irisin also helps prevent or overcome insulin resistance, which leads to type 2 diabetes.

No need to wait
The possibility of creating a new medication based on irisin for weight loss or type 2 diabetes may have pharmaceutical companies already mapping out the long, expensive process for bringing a new drug to market. But you can make your own irisin today, for free, by exercising. And even if irisin’s effects aren’t quite as potent in humans as they are in mice, you are still getting all the other benefits that exercise has to offer.

Keeping it fresh

Want to change the way you experience exercise? These tips can make workouts more enjoyable.

1. Set your own calendar. Bored by the same-old, same-old schedule of exercise? Mix up your activities and time spent on each. People who plan ahead are more likely to follow through. So, once a week, pencil in your choices on your calendar. Carving out room for several short daily stints is often easier than one lengthy bout of activity. Three 10-minute blocks on Tuesday, one 10-minute block on Wednesday, two 10-minute blocks on Friday, plus a 90-minute hike or bike ride on Saturday meets aerobic goals for the week. Choose combinations and activities that appeal to you. Remember, though, it’s best to be active at least three days a week.

2. Wear a pedometer. The simplest step-counter can up the ante on exercise, according to a 2007 Journal of the American Medical Association review of 26 studies. Over all, those who clipped on a pedometer raised their physical activity by nearly 27%, adding about 2,100 to 2,500 steps a day. Other results were promising, too: a drop of 3.8 mm Hg in systolic blood pressure and a decrease in body mass index. Setting a step goal counted for a lot. Those who did so significantly increased activity; those who didn’t generally remained at baseline.

So it may be worthwhile to invest in a pedometer and to set a step goal for yourself. To translate aerobic exercise guidelines from the page to the pavement, aim for 3,000 steps in 30 minutes — that’s 100 steps a minute. Five days of this (or three days of 5,000 steps in 50 minutes) enables you to meet your weekly goal of 150 minutes of moderate aerobic activity. Can’t find a chunk of free time that long in your schedule? Try 10-minute chunks — that is, 1,000 steps in 10 minutes — throughout the week.

3. Plug in. Turn on your computer and power up with the great range of individual exercises and workouts on these websites:

• American Council on Exercise (www.acefitness.org/exerciselibrary) Browse an extensive library of exercises sorted by ability level, muscles targeted, or equipment needed, then view selected exercises in motion.
• Centers for Disease Control (www.cdc.gov/physicalactivity/everyone/videos) View video clips describing intensity levels as well as aerobic and strength exercises for home and gym. Easier variations on strength exercises are included.
• Shape Magazine (www.shape.com) Create an account and log on for a free virtual trainer, which helps you plan workouts and track progress, plus access to free workout videos.

Or go interactive with a video game. Change up your weekly exercise routine by balancing, bowling, boxing, or trying any number of other active options available through Wii Fit and Wii Sports. Or work up a sweat stamping out the beat to music videos on Dance Dance Revolution, a video game that is available for PlayStation, XBox, and Wii.

4. Rise to the challenge. If your workouts aren’t challenging or interesting enough, expand your horizons. The Presidential Active Lifestyle Award and Presidential Champions challenge (www.presidentschallenge.org/celebrate) encourages you to become more fit.

The Presidential Active Lifestyle Award helps you set activity and healthy eating goals over the course of six weeks, while the Presidential Champions challenge allows you to earn points for all sorts of activities: badminton or baton twirling, jai alai or juggling, ski jumping or skydiving, along with many more plebian pastimes. The more effort an activity requires, the more points you rack up while doing it. Log in alone or as a group (you can start your own group or join an existing one) to track your progress toward Bronze (40,000 points), Silver (90,000 points), and Gold (160,000 points) medals. There’s even a Platinum medal for those earning 1 million points. (Point requirements are higher for advanced athletes.)

Sources:
www.health.harvard.edu