By GINA KOLATA
Published: December 20, 2007
The New York Times
THE Spinning class at our local gym was winding down. People were wiping off their bikes, gathering their towels and water bottles, and walking out the door when a woman shouted to the instructor, “How many calories did we burn?”
“About 900,” the instructor replied.
My husband and I rolled our eyes. We looked around the room. Most people had hardly broken a sweat. I did a quick calculation in my head.
We were cycling for 45 minutes. Suppose someone was running and that the rule of thumb, 100 calories a mile, was correct.
To burn 900 calories, we would have had to work as hard as someone who ran a five-minute mile for the entire distance of nine miles.
Exercise physiologists say there is little in the world of exercise as wildly exaggerated as people’s estimates of the number of calories they burn.
Despite the displays on machines at gyms, with their precise-looking calorie counts, and despite the official-looking published charts of exercise and calories, it can be all but impossible to accurately estimate of the number of calories you burn.
You can use your heart rate to gauge your effort, and from that you can plan routines that are as challenging as you want. But, researchers say, heart rate does not translate easily into calories. And you may be in for a rude surprise if you try to count the calories you think you used during exercise and then reward yourself with extra food.
One reason for the calorie-count skepticism is that two individuals of the same age, gender, height, weight and even the same level of fitness can burn a different amount of calories at the same level of exertion.
Claude Bouchard, an obesity and exercise researcher who directs the Pennington Biomedical Research Center in Baton Rouge, La., found that if, for example, the average number of calories burned with an exercise is 100, individuals will burn anywhere from 70 to 130 calories.
Part of that is genetic and part is familiarity with the exercise. The more familiar you are with an exercise, the fewer calories you use at the same level of effort, he found in a research study. Subjects rode stationary bicycles six days a week for 12 weeks. They ended up burning 10 percent fewer calories at a given level of effort after their training. The reason, he said, is that people perform an exercise more efficiently as they become more accustomed to it.
There also is a seldom mentioned complication in calculating calories burned during exercise: you should subtract off the number of calories you would be using if you did nothing. Almost no one does that, Dr. Bouchard said. But for moderate exercise, the type most people do, subtracting the resting metabolic rate can eliminate as much as 30 percent of the calories you think you used, he added.
Resting metabolic rates, though, differ from individual to individual and also differ depending on age, gender, body mass, body composition and level of fitness, so guessing at your resting rate also is fraught with error.
Even if you wanted to get a rough estimate of the calories an average person your size might burn at the gym, you might not want to trust the displays on cardio machines, with the possible exception of treadmills, said William Haskell, an exercise physiologist at Stanford. And with treadmills, the calories are not accurate if you hang on the bars.
Dr. Haskell once studied people using treadmills. Hanging onto the rails reduced the number of calories burned by 40 to 50 percent. The same thing happened with stair-climbing machines.
“I’ve seen people hanging on stair climbers who think they are doing 1,200 calories an hour,” Dr. Haskell said. “They probably are doing 600 calories an hour.”
As for the calorie counts on machines like stationary bicycles and elliptical cross trainers and stair climbers, all bets are off, researchers said.
A major problem is that the machines get out of calibration. “They drift in speed and grade,” Dr. Haskell said. “If you go from one machine to another, it is obvious that at the same setting you are working much harder on one and much less on the next.”
Another is that the companies use their own formulas to calculate what an average person of a given size will burn at a given level of intensity. And those formulas may vary by company as well as by machine.
Jim Zahniser, a spokesman for Precor, cautions that the company’s machines are not supposed to give the exact number of calories for you. Instead, they are estimates of the calories an average person would burn at that work level. And, the company explains on its Web site, there is no easy way to know whether you are that average person.
“Unfortunately, there are as many answers to that question as there are people,” Precor said on its Web site. As for calorie charts, which tell how many calories a person burns when running a distance at a rate of a 10-minute mile, for example, or walking at a rate of a 15-minute mile or riding a bike at 15 miles an hour, the same difficulties apply.
“If any company told you the calorie counts on their machines would be dead on, they’re lying to you,” said Mike Armstrong, a spokesman for Nautilus. “There is some error, there is some play,” Mr. Armstrong said. He advises that when you look at the calorie count, “take it with a grain of salt.”
Christa Dickey, a spokeswoman for the American College of Sports Medicine, which publishes such a chart, cautions that figuring out calories “is always a bit of a challenge since you can really only assign estimates.”
Some say to just forget estimating calories and focus on why you exercise in the first place.
Philip Clifford, a physiologist at the Medical College of Wisconsin in Milwaukee, learned that lesson a decade ago.
In a study published in the Journal of the American Medical Association, he asked whether people’s estimates of how hard they were working were related to how hard they actually worked on a stationary bike, a rowing machine and a treadmill. He discovered that people who said they were putting out the same effort on the rowing machines and bikes as on the treadmill actually were burning many fewer calories.
But for most people, calories burned should not matter, Dr. Clifford said.
“It all depends on what your goals are,” he said. His aim is to get some exercise, preferably outdoors. Calorie counts are beside the point, he said, and he would not believe them anyway.
Yet it is almost too tempting to assume that the calorie counts on machines and in charts are correct.
One of my running partners, Jennifer Davis, took the charts a little too literally when she was in college. She decided to try eating the exact number of calories she calculated she should require according to her activities — she ran and was on the Dartmouth crew. She ended up losing so much weight so fast she was alarmed. She halted her experiment.
It’s more common, though, to make the opposite mistake, exercise physiologists say, greatly overestimating the number of calories you used.
My husband and I will never forget a mathematician at a meeting we attended when we were graduate students. He proudly announced that he could eat a piece of pie because he had just run a quarter-mile on the track. (At 100 calories a mile, he might have burned 25 calories running. A piece of pie could easily contain 400 calories.)
Dr. Bouchard said he regularly sees people at his gym who boast about fantastic numbers of calories they believe they burned. Usually, he just bites his tongue.
“I don’t want to discourage them,” he said.
Sometimes, though, with people he knows well, he tries to tell them that the counts are way too high, and why.
“They look at me in disbelief,” Dr. Bouchard said.
No Gimmicks: Eat Less and Exercise More By JANE E. BRODY
Published: January 1, 2008
The New York Times
A desire to turn over a new, more healthful leaf typically accompanies the start of a new year. My mail, for example, has been inundated with diet books, most of which offer yet another gimmick aimed ultimately at getting the gullible reader to eat less and exercise more.
Publishers assume, correctly, that the shock of the scale after nearly six weeks of overindulging on food and drink will prompt the purchase of one or more books on dieting by people who are desperate to return to their pre-Thanksgiving shape.
And really, it doesn’t matter whether you choose a diet based on your genotype or the phases of the moon, or whether you cut down on sugars and starches or fats. If you consume fewer calories than you need to maintain your current weight, you will lose.
My advice here is to save your money, toss out (or donate to a soup kitchen) the leftover high-calorie holiday fare, gradually reduce your portion sizes and return to your exercise routine (or adopt one if you spent too much of ’07 on your sofa).
Slowly but surely the pounds will come off. And as Aesop said, slow and steady does indeed win the race. Gradual weight loss, achieved on an eating-and-exercise regimen that you can sustain indefinitely, is most likely to be permanent weight loss.
If you’ve been reading this column for years, no doubt you already know that. But I believe it bears repeating at least once a year, not because I want to further depress the booksellers’ market, but because I’d rather you spend your hard-earned money on foods that can really help you achieve and maintain a healthy weight and good health.
The basics of good nutrition have not changed.
Meals replete with vegetables, fruits and whole grains and a small serving of a protein-rich food remain the gold standard of a wholesome diet. Still, at both ends of the age spectrum as well as in between, recent months have held some new findings — and some surprises — that are worth noting.
Perhaps most distressing to a chocoholic like me was a report in the Nov. 20 issue of the journal Circulation that while dark chocolate can indeed improve coronary circulation and decrease the risk of heart-damaging clots, most dark chocolate on the market is all but stripped of the bitter-tasting flavanols that convey this health benefit.
The color, in other words, tells you nothing. Now it’s up to manufacturers to label the flavanol content — not just the percentage of cocoa, which may have no flavanol at all.
Focus on Brain Food
As the population ages and the prevalence of dementia rises, increased attention has focused on how diet may help keep cognitive decline at bay. A heart-healthy diet that keeps clogged arteries from limiting the brain’s supply of oxygen and nutrients has been linked to a lower risk of dementia.
Likewise, omega-3 fatty acids in fish and fish oil, which counter inflammation, appear to protect the brain as well as the heart and joints. A recent analysis of 17 studies in the journal Pain found that daily supplements of these fatty acids significantly reduced inflammatory joint pain.
But now there may be a new kid on the block: vitamin B12. A 10-year study with 1,648 participants in Oxford, England, found an increased risk of cognitive decline in older adults who had low blood levels of vitamin B12. This vitamin is found only in foods from animals, yet it is common for older people, especially those on limited budgets, to cut back on foods like meats and fish.
Strict vegetarians, who have long been cautioned to take B12 as a supplement to prevent a deficiency, can add brain protection to the list of potential benefits. The rest of us should feel comfortable about eating red meat and poultry as long as it is lean and consumed in reasonable amounts. A serving of cooked meat, fish or poultry is only three to four ounces.
The British researchers noted that high blood levels of homocysteine had previously been linked to an increased risk of Alzheimer’s disease, and that B12 is one of the vitamins, along with folate and B6, that lower homocysteine levels. However, the researchers found no benefit to cognitive function from folate.
Foods to Fight Cancer
Here we come full circle. A decade after the American Institute for Cancer Research issued its first major report on diet and cancer, a new magnum opus in concert with the World Cancer Research Fund was published late last year. Based on 7,000 studies of 17 kinds of cancer, it concluded that being overweight now ranks second only to smoking as a preventable cause of cancer. “Convincing evidence” of an increased risk resulting from body fatness was found for cancers of the kidney, endometrium, breast, colon and rectum, pancreas and esophagus.
Other major findings of increased risk included red and processed meats for colon and rectal cancer, and alcoholic drinks for cancers of the mouth, throat, larynx, esophagus, breast, and colon and rectum.
“Convincing evidence” for cancer protection was found for physical activity against colon and rectal cancers, and for breastfeeding against breast cancer. “Probable” protection against various cancers was also found for dietary fiber; nonstarchy vegetables; fruits; foods rich in folates, beta-carotene, vitamin C and selenium; milk, and calcium supplements.
Caffeine is absorbed through the lining of the stomach, which increases your stomach acid production and may put you at greater risk for developing a stomach ulcer. Caffeine acts as a stimulant for the central nervous system, which can make you hyperactive and restless, alter your heart rate, and may interrupt your sleeping patterns leading to an increase in insomnia. And too much caffeine may increase a pregnant woman’s risk of miscarriage.
