Q. Please talk about saunas and steam rooms. Are they good or bad? One instructor told me that I'd lose fat by using the sauna. Is this true? Would you recommend that I use one? How much time per session?

S.C.

Rockville

A. While a sauna uses dry heat and a steam room uses moist heat, they have the same purpose -- making you sweat.

Women normally prefer the sauna because it apparently doesn't take body from a hairstyle the way a steam room does. You may also find it a little more difficult to breathe initially in a steam room. But you should try both and decide for yourself.

I wouldn't recommend them if you have a heart condition or are extremely obese. Your doctor could better advise you if you have any health complications.

But I think they're good if used for the right reason -- to relax. The heat soothes the body. It makes you sweat, so a shower or dip in the pool normally follows, and that can be refreshing and invigorating.

That's the only reason I'd recommend a sauna or steam room. Physiologically, they do little good. If your muscles are stiff and sore, or you're mentally or physically tired, they have a comforting placebo effect but no real medicinal benefit.

The wrong reason to use a sauna or steam room is to lose weight. Unfortunately, that's why many misinformed porkers cook their bodies, hoping to melt away the fat.

Water makes up approximately 60 percent of an adult's bodyweight. The sweat mechanism is a safety valve for the body, not a means to lose weight. You're being fooled (or a fool) if you believe you're losing fat by sweating. You're simply losing water. It is a temporary weight loss.

Weigh yourself before going into the sauna and again when you come out. If you lose two pounds by sweating, you should replace that watr loss immediately. And if you don't do it right away, the process of hydration will take place as soon as you drink any fluid during the course of the day.

Athletes often misuse the sauna. They starve themselves and then dangerously dehydrate their bodies before competition, in an attempt to make a weight class they probably shouldn't be competing in.

Dehydration -- through saunas, steam rooms, rubber suits or body wraps -- disturbs the body's fluid and chemical balance. Electrolyte (sodium, potassium, calcium, chloride) levels are disrupted. This diminishes coordination, strength, muscle endurance and performance. And who knows what long-term effect it might have on the normal growth process?

The instructor who said you can lose fat by sitting in a sauna is technically correct. So are those ads that rip you off by telling you that you can lose weight (if you buy their product) while sleeping or watching TV.

This kind of "weight loss" is accomplished through your basal metabolic rate (BMR).abolism is the process of breaking down food for energy. Fat is a stored source of energy. At rest, your body requires a minimum amount of energy to sustain life. This is called your BMR. This energy-burning process takes place 24 hours a day.

Technically, you can say that you are burning fat 24 hours a day through your BMR. It occurs while sleeping, eating, watching television, and even while basting in the sauna. So your instructor and those ads are technically correct. But remember, the sauna or those quacky devices are not forcing you to burn any fat you wouldn't already be burning.

How long should each sauna session last? The more you sweat, the shorter the session should be. (Or be sure to drink while you sweat). People react to heat and saunas differently. Some feel light-headed or dizzy. During your first session, stay for just a few minutes to determine if you are affected adversely or not. If not, increase the length of each session accordingly. I think a reasonable and conservative guideline would be 10 to 15 minutes total.

Give it a try. Most people aren't adversely affected and enjoy using the sauna. But remember why you're using it, if you want to be fitness "per-sauna-fied."