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?

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 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?

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'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)?