I recently lost about 40 pounds in three months (an average of between two to three pounds a week). To lose weight, you must burn more calories than you eat each day. It’s really that simple. It’s all about mass-energy equivalency.

One pound of fat equals 3500 calories. This means that if I eat 500 calories less than I burn every day, I will lose on average one pound each week. 500 calories per day times 7 days equals 3500 calories per week. That’s a nutritional fact I’ve known for many years, but never put into practice until 2012. My nutrition and exercise plan since February 1st has been to eat about 1500 calories a day and to burn about 3000 calories. In theory that means I would lose about 3 pounds a week. In the first 17 weeks of this plan, I lost almost that amount, about 40 pounds.

“How did you do it?”

This is the question many people have asked me recently as if there is a trick to it. I tell them, “You need to burn more calories than you consume.”

The difficulty, of course, is in knowing exactly what you eat each day and how many calories you burn. The correct question to ask is:

“How can I be sure I am burning more calories than I eat each day?”

I log all the food I eat on-line at www.fitbit.com and I wear an exercise monitor that estimates the calories I burn each day. I had to become committed to doing at least a certain amount of exercise every day and logging everything I eat.

First a little background – I’ve always had a large frame and carried my weight well, but I never was seriously overweight until I was about 27-years-old. For a year after my 26th birthday in 1988, I worked as a laborer for a construction company that built solariums. I was working outside all day in the cold and heat and was consuming a lot of calories. Consequently, I put on about 15 pounds that year. I excused this by rationalizing that it was mostly muscle mass I gained through physical labor.

A year later, I began working as a teacher, a much more sedentary job. I tried to compensate by walking, jogging and going to the weight room a few times a week. But since I continued to eat a lot of calories, I put on another 15 pounds that year. I realized one day in the summer of 1989 that I had begun to look fat. So I began walking and running a few times a week and eventually lost about 20 pounds.

The maximum weight according to health experts for a male of my height and frame is 185 pounds. Several times in my life I have made a serious attempt at getting into better shape. Each time I lost at least 20 pounds, but I never got to my optimum weight. These were the “high water marks.” I weighed 220 pounds in 1989, 237 pounds in 1999 and 255 pounds in 2011. Each time I lost weight, I eventually gained back more weight than before.

While exercising, I made a change in eating habits for a set period of time. But since I did not make a permanent change, I would eventually gain back every pound and then some. Although I have heard this many times before, and you probably have too, the truth is that diets don’t work. A diet is a temporary strategy to lose weight. I’ve eliminated the word “diet” from my vocabulary in discussing weight loss. If I don’t enjoy the foods I am eating and feel deprived by hunger or lack of enjoyment, the diet is not going to last very long. The key is understanding nutrition and a lifelong plan.

Another bit of background about me is that although I enjoy sports, I am not an athlete by any stretch of the imagination. I don’t enjoy pushing myself to my physical limits. A little recreational exercise is fun for me, but a lot of exertion is not. One of the problems with working hard to lose weight is that unless it is something I enjoy doing, I am not going to do it every day without fail for a long period of time. The key here was to find some type of exercise I could do every day without exception.

What I need to maintain weight loss is proper nutrition and exercise over my entire life. The key is knowing what I am eating each day and knowing how many calories I am burning. I found that Fitbit provided the means to keep track of everything easily.

In part 2, we will look at several popular fitness and nutrition myths.