While many overweight people find it difficult to shed extra pounds, those who are underweight face their own challenges trying to keep each pound and add more. The good news for those trying to gain weight is that adding pounds can be simplified.

Why is it so tough to gain or lose weight?

When I was under-30, I weighed in at 142 lbs at 5 feet 8 inches. I was pretty lean and could everything that wasn't nailed down, withour gaining an ounce! I wanted to gain weight in the worst way but there just wasn't information available about how to do it. When I crossed the 30 mark, mysteriously I began to put on weight.

Actually, it's no mystery. My metabolic rate is what was responsible. It simply slowed down after 30.

Your metabolism is responsible for regulating the rate at which your body consumes food or stores food as fat on your body. If you have ever wondered why some people are able to pig out and never gain a pound, or why some people put on several pounds simply by pigging out a couple of times, the answer lies in your body's metabolism. The more efficiently your metabolism functions, the more efficiently it burns through calories. It follows then, the more you understand how to manipulate your metabolism, the easier it will be to gain weight.

Weight gain can come from eating more rich, tasty foods, a decrease in activity level, or a subtle change in the rate that your body burns calories. Studies show that even the most inactive people can gain significant health benefits if they accumulate 30 minutes or more of physical activity per day. Whether you are trying to lose weight or gain it, you should understand the important role of physical activity and include it in your lifestyle.

Genetics and other factors affect how your body uses the calories you consume. Still, the only way to gain weight is by taking in more calories than you burn.

In a study of holiday weight gain, people who reported being much more active maintained their weight or even lost weight during the holidays. Those who reported being less active gained the most during this period.

Gaining anymore then 1 or 2 pounds a week is unhealthy and means you're putting on way to much fat. So look for 1 or 2 pound gains at the end of the week. Doesn't sound like much? It works out to gaining 5-8 pounds a month!

So, you want that perfect bod? First, ask your doctor! Do it yourself weight manipulation can cause serious health problems. You knew that, right?

A good approach might be to venture into the bodybuilding community. There you will find many people, like you, also seeking ways to put on lean muscle mass. You will also find many products marketed to help you gain weight. Be very cautious when looking at these products. Gaining weight may not be as in demand as losing weight but it is still big business and there are a lot of companies out there looking to take your money. While some of these products can help, others aren't necessary.

Again, always ask your doctor before trying to become the next Ms. or Mr. Universe!

Jim DeSantis Jim DeSantis is a retired investigative reporter who now blogs full time. Jim has created a Free Report containing 5 Free Quick Start Body Shaping Plans here. No Email Required to get it. Jim also publishes a Health Blog here where you'll find a wealth of free health and fitness information.