I Walk. Why Can’t I Lose Weight?

Q: I’ve been walking with a friend five days a week for 90 minutes to two hours. We’ve been doing this for around eight months, but neither of us has lost any weight. We don’t diet, but try to be careful of what we eat. What can we do to lose weight?

A: Losing weight from exercise alone takes time, but it can be done. That said, it takes an awful lot of exercise hours to burn enough calories to lead to significant weight loss. And the bad news is that there is research that has found that for some women, walking isn’t always enough. But before you jump to the conclusion that walking is a waste of time, consider a few reasons why these studies have failed to produce weight loss from walking, and then ask yourself if some of these caveats apply to you.

Food intake is unknown

Most exercise researchers find it hard to control all the variables that affect weight loss and weight gain—especially what people eat. Unlike mice, which can be kept in a laboratory environment in a cage and fed precisely measured portions of animal chow, humans are not so easily controlled. The best weight-loss studies—those that are long term, lasting at least six months or for several years—have to rely on the subjects being outside the lab.

So scientists are left concocting ways to estimate what people eat. A few studies do have enough funding to actually provide meals to their participants. (Even then, there’s little proof that subjects aren’t sneaking in extra snacks.) But most studies ask participants to fill in periodic food diaries or to recall at different points during a study what they have eaten in the last 24 hours. There are ways that researchers try to ensure that this information is accurate. But these methods only provide rough estimates of what may constitute a normal eating pattern by subjects. So it’s not always possible to know if a few people are eating more or less than they report.

If a study is looking at exercise only, the researchers will often merely advise subjects to keep their diets the same. This is an attempt to ensure that a subject doesn’t diet or eat more than normal, thereby affecting the effects of the exercise. But without following each subject around 24/7, it’s hard to know if the subjects really are maintaining a totally unchanged diet.

You mention that you and your friend are watching what you eat ... but what does that mean exactly? Are you keeping a food diary every day and measuring portions? If not, you could very easily be slipping in a few extra calories that may be thwarting the calorie burn from your long walks. If you and your friend finish your walk with a trip to Starbucks, one coffee drink or muffin can set you back 300 to 500 calories, which might be nearly the amount you burned off during your walk. So, if you’re not losing weight, it might not be that your walks are not working, it might be that you are eating extra calories without realizing it and counteracting the effects of your walk.

Calorie burn is insufficient

Weight loss is about burning more calories than you use. Exercise burns calories, but if you are a light person exercising at a low- to-moderate intensity for a short time, you may not be burning a big chunk of calories. You are walking 90 minutes to two hours—that should definitely be enough to burn a good amount of calories.

How many? Well, depending upon how much you weigh, you may be burning at least 350 to 500 extra calories above and beyond what you’d burn just sitting. If you walk fast or up hills you could be burning more. In eight months, you should have accumulated a sizable enough calorie burn to see some dent in your fat and body weight. Are your clothes looser at all? Is your waist line smaller? If not, it might be because you are making up for those calories with extra food somewhere during the day.

Every body is different

Or you might just be weight-loss resistant due to some fat-loving genes. Of course, the fact that both you and your friend say you have seen no body changes suggests that it might be less genetic and more environmental. Not all studies that show a lack of results spell out the full story. Some studies that show no weight loss among all the subjects fail to point out if there was great individual variation within the study. So while one person may have lost a great amount of weight, a few others may have gained—and when study results are published, only averages of the group are usually reported, not each separate result. It might be that a few people lost more, or didn’t lose, because they were genetically inclined to do so. Or it might be that the person who didn’t lose was sneaking in a Snickers bar that the others were not!

Sedentary behavior adds up

A new area of focus in obesity research is trying to quantify not only how much people eat and how active they are, but how sedentary they are. It turns out that the more sitting you do the greater your risks of weight gain and chronic diseases, even if you do exercise, according to research reported in the British Journal of Sports Medicine. Another phenomenon that has been found is that some people get more sedentary once they start exercising. Whether it’s biologically driven or it’s a psychological compensation (“I exercised today, I don’t need to go up the stairs, I’ll take the elevator.”) is unclear. But make sure you’re not slowing down. Wear a pedometer during all your waking hours and get a sense for how many steps you take throughout the day, and make sure you’re racking up 10,000 to 15,000, including your walks.

Many, many women have successfully lost weight through walking. And the National Weight Control Registry finds that the majority of those in its national weight-loss database report walking on a near-daily basis for an hour or more to help maintain their weight loss. You may need to control your diet intake. But even if you don’t lose weight, you are helping your health in myriad ways and definitely preventing weight gain. Keep it up!

Do you have a fitness or weight-loss question for Martica? Send e-mail to experts@microsoft.com. Please include Ask Martica in the subject line. Each of our experts responds to one question each week and the responses are posted on Mondays on MSN Health. We regret that we cannot provide a personalized response to every submission.

Martica Heaner, Ph.D., M.A., M.Ed., is a Manhattan-based exercise physiologist and nutritionist, and an award-winning fitness instructor and health writer. She has a Ph.D. in behavioral nutrition and physical activity from Columbia University, and is also a NASM-certified personal trainer. She has written hundreds of articles for publications such as Self , Health , Prevention , The New York Times and others. Martica is the author of eight books, including her latest, Cross-Training for Dummies. (Read her full bio.)

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