Why is it I can always run a greater distance on a track than I can on a treadmill? On a track, I can run five or six miles, but on a treadmill, I can only go a maximum of three or four, then I tucker out. Is it because I get more bored on a treadmill, or is there a more physical explanation?

I have been chewing and spitting large amounts of food (pretty much always sweet stuff — pastries, chocolate, etc.) almost every night for eight or nine months. I am eating a healthy, balanced diet otherwise, maybe a little on the lower caloric side (1300 to 1500 calories per day). My chewing and spitting sessions usually follow a balanced meal. I know this is a type of eating disorder. I have done a lot of research online and I know that there are side effects, although they vary depending on who you ask. Some sites mention that chewing and spitting activates the release of insulin and results in hyperinsulinemia, insulin resistance and weight gain. Is this true? How long would it take to develop these problems? Are these reversible if I were to stop this behavior?

I'm curious to know if going to the gym increases sexual drive? I am a female in my 20s and recently started an exercise routine (running and weights), and I have noticed that my sexual drive has increased significantly. There have been no other major changes in my life, and I have been dating the same man for close to two years now, so I can think of no other real reason why my libido would have increased. Is there any real connection between working out in the gym and beneath the sheets?

I've heard of body suits that increase sweating during exercise. Then I heard that Saran wrap had the same effect. I want to shed pounds but first I wanted to know if wrapping plastic wrap around the stomach helps burn fat during exercise.

What is the best way to prepare, health wise, before a big test such as the SAT, LSAT, MCAT? What foods do you recommend to keep my "brain moving?"

Does altitude affect calorie-burning? That is, if I do the exact same workout twice — once in New York City and once in Colorado — will I burn more calories at the high altitude? What things DO affect how many calories you burn in a workout?

I have heard that if you exercise/work out in the morning before you eat breakfast that it will cause your metabolism to increase throughout the day, helping you to burn calories. Is this true?

I've read a lot lately about midnight snacking and late night eating and obesity and calorie worries, but my problem lies in the opposite direction — I'm LOSING weight, and insatiably hungry, day and night! The only advice I get is, "Eat healthy," which is preaching to the choir, since I consume more fresh produce, mostly vegetables, and home-cook all my own meals. At a recent nutrition check-up, the nutritionist patted me on the back in congratulations for having one of the healthiest lifestyles he's seen, and shrugged at my inexplicable hunger. The fact is, I'm in the kitchen every other hour, and my body doesn't differentiate between awake and asleep anymore when it comes to hunger. I go to bed on a full stomach, and wake up every three hours to eat again. It's exhausting! I'm falling asleep during the day — but never more than an hour, because hunger strikes. And amid all this, my grocery bill climbs and my weight drops. I don't get it. What am I doing wrong?

A friend of mine and I were disagreeing about this point and I thought maybe you could help. I have heard that it is not possible to both lose fat and build muscle mass simultaneously: ideally, a person should do cardiovascular exercise with dieting to lose extra body fat, and then start to focus on building up muscle mass. He says it's possible to both burn fat and build up muscle over the same period of time. Which is the case?

I have a question about walking for weight loss. My walking buddy believes the theory of walking distance is what helps you lose weight best versus my theory that it is the speed at which you walk that matters. So, could you help me figure this one out? Which matters most in ultimate weight loss: speed or distance?

When working out in the gym, machines, such as treadmills and stationary bikes, show how many calories you are burning. Are these calculations correct, or is it just something to keep the participants happy?

What are the advantages of eating five or six smaller meals per day, as opposed to three meals per day? I've heard it helps to lose body fat. Also, are there advantages to eating more of your calories early in the day?

1) A friend and I were discussing this. We both try to stay healthy by eating well (high fiber, low fat, lots of veggies, fruit, etc.) and living an active enough lifestyle (hiking, rock climbing, biking, etc.) that we stay in shape. The question we have, then, is what the current "rules" are for appropriate weight/height ratios? Or are such measurements now thrown out in favor of body fat percentage measurements? She's 5'1" and I'm 6'1" and we're curious what the medical rule of thumb would be for how much each of us "should" weigh...mostly because we're wondering if it takes into account things like muscle mass. What would the current medical/health industry recommend each of us weigh? Are these numbers accepted or are they seen as not as important as they might have been 20 years ago. If you have actual numbers, we'd be curious to see that too. Thanks! I have a dinner riding on this!

2) Could you clarify the Body Mass Index deal? According to one BMI chart, I am "slightly overweight" because I am 5' 5-1/2" tall and weigh 160 lb. I am also very muscular and have a large frame. The lower BMI readings are labeled "ideal," but I've heard muscle weighs more than fat, so if the chart does not include the muscle factor, is it basically saying that it's "ideal" NOT to have extra muscle? I look slender and have never been told by a doctor to lose weight. I'm a twenty-four-year-old female, lacto-ovo-vegetarian, and get lots of exercise, including walking and frequent "sweaty" workouts.

After practicing yoga in normal temperatures for years, I recently attended a heated yoga class (heated quite hot: 95 to 100 degrees!). The experience left me dizzy, nauseous, and completely enervated. Afterwards, I expressed my concern to the teacher, asking why the studio needed to be so hot. She "explained" that by sweating, supposedly the body releases "toxins" and that my nausea and dizziness must indicate that I need to "detox." Personally, I think I was suffering from heat exhaustion. I've heard this silly explanation more than once, as many people seem to believe toxins are released through sweat. But is that true??? And — next question — doesn't exerting oneself in extremely hot temperatures seem like a recipe for dehydration? Are their any benefits that make it worthwhile, or is all this heated yoga just nonsense?

Do "fat burners" really work? If so, why? If not, why not?

I'm a college student and also a bodybuilder. I've become aware of very high protein intake amongst bodybuilders at my gym. I'm skeptical as to consuming as much protein (around 225 grams) a day like the bodybuilders at my gym do. Do bodybuilders need more protein? And if so, how much more?

I have recently learned that in order to burn fat as a fuel, your body requires carbohydrate. Up until this point I had been doing cardio training first thing in the morning on an empty stomach, as I had read that this is optimum for fat burning. However, now I have a small carbohydrate snack before I train in order to prevent my body using lean muscle tissue as a fuel. Today I have again read in another book that training on an empty stomach first thing in the morning burns the most fat. I am a little confused over the best thing to do! I train with weights twice a week and do cardio three times per week. I do want to maintain my lean muscle, but am looking to reduce my body fat.

Is it bad to exercise while slightly drunk? Some friends like to hike and drink beer. I find that I get flushed easily, and tire more quickly. What's going on?

I am a wrestler and have very great ambitions within the sport. I lift weights for five to six hours a day, making sure I perform every set to failure often including negatives as well. In addition to working each muscle group two times a week, I make sure to give each muscle group 48 to 72 hours of rest. Recently though, I have learned that training longer than an hour a day can have a catabolic (muscle breakdown) effect on your body. This was very concerning to me because muscle-wasting during my training seems truly counter-productive, but I am also aware that a decrease in training may lead to muscle atrophy and that also poses a deep concern. I have also learned that cardio and even sleep can have a catabolic effect. I will have to cut my training time eventually due to time restrictions during the season because of school day and team practices, including traveling time and homework. I am posing a couple of questions within this letter: 1) Can I reduce the volume of my routine to about an hour and still make gains that are comparable or better to those I experience with my five to six hour workouts and if so, how? 2) Is catabolism truly a legitimate matter to be concerned with?

I've been told that every two to three weeks, I need to change my weight training routine or else my body will become too accustomed to it and I will stop seeing results. Is it really necessary for me to change my entire routine, or do I only need to increase weight and/or repetitions?

My friends and I disagree — can you settle the dispute? I feel a calorie is a calorie no matter what time of day that you eat it. They say that if you eat all of your calories early in the day, that it is less fattening, because you will be moving around burning off those calories. I say that if you eat 1800 calories a day, it doesn't matter if you eat them in five meals or ten meals, it is still 1800 calories. I believe that the idea of not eating anything after 7 p.m. helps you to lose weight because you cut out the high calorie, high fat foods that are often eaten late in the evening. They say that by not eating after 7 p.m., you lose weight because you're not moving to burn off those calories. Please settle the dispute. Thanks.

My husband and I are having a debate over the value of liposuction as a means to permanent fat removal. He has read that we are born with specific number of fat cells and therefore believes liposuction has the ability to reduce the number, resulting in permanent fat loss in the areas that are surgically treated. I differ in the belief that fat loss and its permanency depends on maintaining and correcting diet that is related to metabolism. I also maintain that there is no such thing as permanent fat loss from liposuction. Have you an answer to our debate?

Hot yoga is becoming more popular every day but there is a lot of conflicting information regarding benefits versus injuries. Most of the information does not quote sources and is therefore is difficult to follow up on. It has unquestionably helped me become a more flexible person but there is a lot of information on the net regarding horrific injuries including slipped discs, muscle tears, neck injuries, emotional problems, and even strokes. Is there a research-based, or at least a factual breakdown on the health benefits of stretching at temperatures above body temperature versus the injury risk of exercising at temperatures above body temperature?

I was bulimic for about four or five months and went from 5'6.5" at 115 pounds to 95 pounds. I have not told anyone, and will not, so please don't ask me to, but I am back up to 110 to 112 pounds and pretty much graze throughout the day so I don't throw up. I mostly snack on white bread, fruit, potatoes, and cereal in large portions, but want to stop and eat a healthy, more balanced diet. The problem is, I am not sure what a healthy weight should be. Charts say I am too skinny, but I don't believe it because I know girls in the media are thinner than me and they seem fine. I want to be as small a weight as possible without being unhealthy. I skipped my period for three months but did get it in January. I have not lost any weight since then though, and I should have gotten my period about a week ago but didn't. I don't understand, it is so confusing, can you help me?

I'm an athlete, and about a year ago, I purchased one of those ab rollers. One time, I was going through the motions and I experienced an orgasm. Now, it happens about every time I use it. I thought it was extremely weird, but then read where women experience orgasms through lots of things. I was just wondering how it is possible for those feelings to happen just by working out my abs. Also, what are some other weird ways that women have had orgasms? Thanks so much.

I've been trying to diet for over two years. My goal is to lose about 25 pounds, but the most I've been able to get is 15, and I can hardly keep it off. I concentrate on eating very little and since exercise is so hard to keep up, I pretty much starve myself to death. I manage to maintain the weight for a month, and then I lose control again. I've been thinking about the various diet products in the market, such as diet teas, herbs, meal- substitution shakes, and other medical products. I'd like to know what kind of side-effects they have, and how effective they are. (Some boast a seven-day plan, but that seems hardly believable.) Also, I'd like to know how well-researched the information is on these products (i.e., are they long-term enough to cover all the side-effects?) As for aspartame, is it really harmless, or is it just not researched yet?

I wanted to know how many days of rest is recommended between workouts. I heard it was three days on to one day off...is this enough? I workout on a treadmill for 50 minutes every day and have for the last 14 months. I was not aware of how rest played a very important role until I recently read a brief article on it. I guess my question is, do I need to take that day of rest and how important is it?

I am a female, five feet tall and about 127 lbs. I am not satisfied with my size. I am not obsessed with weight but with the way I look. I am very strong and have plenty of muscle. It just happens to be covered by a thick layer of fat. Yes, it runs in my family. On my father's side everyone has trouble with their weight.

I am writing to you because I don't understand why I am not losing weight. I am a vegan. I have no dairy products and no fat content in my diet. Except for the occasional pat of margarine and fried falafel, I don't see why I haven't lost weight because I just cut the dairy products out about two months ago. I have been a vegetarian for 9 years. I ride a stationary bike twice a week in my target heart rate zone. I work out with weights and do calisthenics in my room every night. What is wrong? Is there another factor I am not considering? Glands? Do I just need to be patient? I like being big, I just don't want it all to be fat.

Thank You.

Is there any danger to taking ephedra (ma huang) for weight loss?

I'm a 22-year-old woman. Many of my friends in their late 20s and early 30s (and older) have been warning me about an inevitable metabolism slow-down and subsequent weight gain around my 30th birthday. They say, "You just wait. When I was your age, I sat around all day eating pizza and I never gained a pound. Now I can't lose weight no matter what I do."

I am sure there's some truth to this, but I DON'T sit around eating pizza all day. I run three to four times a week and eat very healthfully. Will these habits ease the slowing down of my metabolism? Or should I expect some weight gain no matter what I do (as they say will happen)?

A friend of mine bought me a month's worth of yoga classes over the summer. I loved it! I've never found an exercise/fitness regimen that I actually WANTED to stick with. It helped with a lot of my long-standing physical issues (balance, back pain, stress, fatigue) and was a perfect balance of stretching and strengthening for my fitness goals. The only problem is that now that my month is over... I can't really afford to do it anymore. I've looked all around for inexpensive and conveniently located studios, but I can't find anything that's in my price range or fits in my schedule. What resources are there for broke aspiring yogis? Are there any guidelines for practicing yoga at home? Are there any exercise routines that are similar to yoga (i.e., low impact, stretching + strengthening) that are less expensive or easier to do without an instructor?

I know there are video games out there now that require you to move more, unlike traditional video games. Are these games, like Wii Fit, a good way to be more active or are they doing more harm than good?

For as long as I can remember, I've been using my back muscles when I did sit-ups. In fact, I distinctly remember the first time we did them in second grade. After a few reps, it was already so painful that I was having trouble breathing properly. Being eight years old, however, I didn't realize this was a warning sign and assumed it was normal.

Flash forward ten years, and I have almost no strength in my abdominal muscles. I've tried to teach myself to do curl-ups properly, but no matter how hard I try, I can't even lift my head without using my back muscles. Exercise balls are no help either. Even when I concentrate on using my abs to keep myself steady, my back is still doing 95% of the work.

So, in short, I have two questions: Am I at risk for having damaged my back from years of abuse, and how can I work on strength training my abs now?

I have bowlegs. It is quite frustrating because I cannot do exercises that isolate and tone the thighs (lunges, squats, etc). When I do squats, my pressure/force comes from the calves and the knees, but not the thighs. Reason being is that the legs are not properly aligned, and pressure/force cannot go up to the thighs. It even hurts when I do squats because they involve bending the (crooked) knees. Are there any alternative thigh exercises?

I am 18 years old and I am determined to lose a few pounds and tone my body by the end of May. I just began running and I'm starting off by running a mile and hope to work up to a four-mile run four or five days a week. My diet is generally a bowl of cereal in the morning, and a turkey or ham sandwich with some type of fruit and a bottle of water. Dinner is something different every day, but usually healthy. I also have been doing an ab workout for about seven minutes after I run. Is what I'm doing effective? What are your suggestions?

I have a job that is largely sedentary — mostly sitting in an office in front of a computer. My partner's work is very physically active. Since we've been living together, food and nutrition have increasingly become a source of stress and conflict. He needs big meals with lots of protein and calories, and I need better portion control with lots of vegetables. We're having real problems with shopping and menu planning. Since we've been living together, I've been gaining weight and he's been losing! Can you give us any advice or direct us to information on how to live and eat together while addressing both of our nutritional needs?

I know most of us have seen the ads to buy various muscle toning equipment that uses electric pulses to "build more tissue" (hypertrophy), and I was wondering what you thought about this way of "toning muscle." Also, if you knew where else I could go to further my research on these sorts of devices?

Thank you very much for your help in advance.

I am very concerned about my eating and exercise habits. I'm a first-year, and since I got here last fall, I've lost about 35 pounds. I've been exercising almost obsessively and eating a rigid, low-fat diet. I try to eat about 2000 calories a day, but still feel hungry a lot (especially in the morning) and still seem to be losing weight at the rate of about a pound a week. I'm 6'0" tall and weigh 133 lbs. right now; my family and friends are all worried and although I keep telling them I'm not sick, I wonder if I am. I've seen a nutritionist in Health Services; she gave me some advice about good nutrition and what I should be eating, and I've been trying to follow her guidelines, but it's gotten very hard for me to know what is a "normal" diet. Am I anorexic? If I am, what can I do to help myself? I know I could never go to counseling; I'm too independent. Can you give me any advice?

About five days ago while I was doing step aerobics I stepped down incorrectly and injured my foot. It turns out, after seeing the doctor, that I cracked a bone on the outer side of my foot and will have to wear a boot cast for about four weeks. My question is, since I can no longer do aerobics, what other kinds of exercises can I do to help me lose weight? I already do weights, abs, and any other type of leg exercise that don't involve me standing, but I don't feel that this is enough and since I am prone to gaining weight easily, I really want to do as much as I can but in a way that I don't aggravate my injury or make it worse.

Do you have any suggestions for me on losing weight? I feel so intimidated going to a fitness center because of the looks I get. I really do. It seems like an individual has to be thin to go into fitness centers now-a-days. I should say some of them are that way.

Can you tell me a way to figure out my basic metabolism?