As someone who does research in nutrition and metabolism, I find it very difficult to get overweight patients to eat less. So the idea of adding something rather than taking away is appealing. Thus, simply getting someone to add exercise to burn more calories is a very doable thing.

As I set the table about the direction of this article, I will need to differentiate between exercises to be healthy and exercises to lose weight. In general, moderate exercise on most days of the week is enough to be healthy. This is very different from exercising to produce enough negative caloric balance to lose weight. As you can imagine, it takes more time and intensity to lose weight.

Types of Workouts
Although there are numerous types of workouts you can do, we divide your basic workout into aerobic, resistance and circuit training.

For the sake of simplicity, aerobic or cardio workout is your typical, get on a treadmill or stationary bike and get the heart rate up continuously for 30 minutes. This is very different from resistance training, or weight lifting, which is typically done in sets of repetitions of specific lifts or motions against resistance. An example is three sets of 10 repetitions of biceps, then three sets of 10 reps of bench press, followed by three sets of sit-ups. Typical resistance training has rest periods between lifts or sets. Circuit training (which can go by many names, some very catchy) is resistance training with minimal to no rest periods between resistance motions. The goal is to combine cardio and resistance training by not letting the heart rate drop during the workout. For example; doing pushups, then running in place, then more pushups, running in place and then doing a different resistance maneuver such as sit-ups. Again, the goal is to keep the heart rate up while doing resistance training. Circuit training is typically no longer than 60 minutes, mainly because it is difficult to last much longer.

The Research
First, the good news: There has been a ton of very high-quality research in exercise and weight loss. The bad news is the majority of it has been done on women. Fortunately, most findings can be applied to men, but many of the experts do feel that there are some differences between how men and women respond to exercise in terms of body weight regulation.

If you were to just count calories when you are exercising, then it would appear that cardio or aerobic workouts would be the best way to lose weight. Simply put, you burn a lot (and I mean a lot) more calories with cardio.

Surprisingly, when looking at calories in, and calories out with exercise, it’s a bit more complicated. IA landmark study examined what would be the best exercise routine to not only lose weight but improve the health of overweight patients with diabetes. Be aware that for metabolic reasons diabetics have a much harder time losing weight, so this study was done in the toughest group I know to get significant weight loss.

Three groups of patients were followed for nine months. Very detailed studies of body fat and total weight loss were followed over this time period. The first group only did cardio or aerobic, the second group only did resistance training, and the third group did a combination of aerobic and resistance training. All sessions were supervised and all three groups did no more than 2 1/2 hours of exercise a week (probably the minimum you can do to lose weight with exercise).

The results were impressive and clearly showed the combination of cardio and resistance training lost more weight and more fat. The group that only did resistance training did not lose much weight but did lose fat (even more fat than the aerobic-only group) and gained muscle. The take home message is that to get the best weight and fat loss is a combination of cardio with resistance training.

Intensity Matters
When I first started in this field (many years ago), I was told about the fat-burning zone and many old treadmills still have this on their display. This fat-burning zone was typically around 55 percent to 65 percent of your maximum heart rate; the idea was not to go above a certain heart rate so that you could just burn fat.

Current research shows this to be old-school thinking and pushing your heart rate higher is better for weight loss. (I have to make a disclaimer here: It is important to make sure you are healthy enough to push your heart rate to high levels. A visit to your primary care doctor can easily answer this.) Many of the current studies coming out now will push participants to 85 percent of their maximum heart rate to get the best weight loss. What is not clear to me is whether you need to keep it at 85 percent. This can be quite taxing and just increasing the intensity and hitting 85 percent for a few minutes then dropping down recover and going back up may be good enough.

Spin class is the aerobic exercise that impresses me the most for getting your heart rate up, and keeping it up. These are hour-long aerobic classes on stationary bicycles with an instructor guiding the group, often done to music. Something about the pounding music, the instructor yelling at you and a room of hot, sweaty bodies seems to keep you going.

I have not said much about circuit training but done correctly it is very intense. When you are lifting weights or doing pushups, your heart rate goes up very quickly. If you keep moving quickly from one exercise to another you will keep your heart rate up. Having a qualified personal trainer is very helpful for this type of exercise; having someone push you to keep your heart rate up can be very helpful. (Again, make sure you are healthy enough to do it.)

Ambient Temperature
There have been quite a few studies looking at the temperature that one is working out in. This first came to light in a study I will call the Housewives of Orange County study. It was a study done many years ago in Southern California with women looking at the best exercise to lose weight. The women were told to do one of three different exercises: walking, swimming or stationary bike with the intent of losing weight. At the end of the study the surprise was that the stationary bikers lost the most weight, losing almost 10 percent of their starting weight. The participants that did the walking came in a close second with about 8 percent weight loss. But the shock was that the swimmers lost no weight at all.

There have been a flurry of studies since, and it appears that the temperature of your surroundings is critical. It turns out you still will burn a lot of calories with swimming or exercise in the cold, but when you exercise in a cold temperature you drive up your appetite. Thus you end up eating more and negating the hard work. This compensatory intake of calories is not seen with exercise at comfortable temperatures (70 degrees and up).

What is in Your Workout Bag?
If you are looking to use exercise to lose weight, be prepared to do both aerobic exercise and resistance training. The amount of time you will need to exercise will depend on how much you eat and your genetics. (Yes, it is quite clear many individuals for genetic reasons will have a harder time losing weight; fortunately exercise can over come much of this.)

A ballpark figure of three to five hours per week is needed to lose weight. The amount of time that you spend doing cardio versus resistance training is not clear but 50 percent cardio and 50 percent resistance training is a good starting point. Personally, I try to lean toward more cardio in the range of 75 percent cardio and about 25 percent resistance training.

This blend of cardio and resistance training can be done any number of ways. A simple way would be going to the gym five days a week and doing a treadmill or stationary bike for 40 to 45 minutes and then lifting weights for 15 to 20 minutes. Another way might be going for a jog three to four times a week and then lifting or doing resistance training twice a week. The last way would be to join a boot camp and do a circuit type training program 45 minutes to an hour three to five days a week.

It really does not matter how you do it, just try to get in a mix of cardio and resistance training three to five hours per week. If finding time is an issue, then circuit training probably gives you the biggest bang for your time spent.

If you are wondering what I do to keep my weight down I have two different routines. If I am traveling I go to the gym in whatever hotel I am staying. I start with the stationary bike for about 30 minutes and check my e-mail. I will then hit the weights and push hard for about 15 to 20 minutes lifting in a circuit. I try to move as quickly as I can from one piece of equipment to another trying to hit large muscle groups and keep my up heart rate. If I am at home my routine is as fun as I can make it; I surf or play basketball to get my cardio and then go to the gym and lift two days a week.