It's pretty simple: If you take in more calories than your body needs you will gain weight. If your body uses more calories than you consume you will lose weight. The trick, of course, is to gain or lose the right kind of weight.

Losing weight is easy: Stop eating or become a contestant on Survivor.

Joking aside, if you burn more calories than you consume you will lose weight. Therefore, all you have to do is eat less---right? Well, not quite.

When you start severely restricting your food intake (dieting) in an attempt to lose weight, your body mistakenly believes it's starving.

In the interest of self preservation, your body fights back by slowing down your metabolism to conserve energy and caloric consumption and starts converting as many calories as it can into fat---which it then stores.

As your metabolism slows down you'll start feeling tired and lazy. You'll also become more irritable because you're depriving yourself of the foods you want and your body of the fuel it needs. Initially you will lose weight---but not in a healthy or permanent way or in the way you think.

Your body will continue adding and storing fat, use what little it needs to survive and even start cannibalizing muscle tissue to function. The more you starve yourself, the worse it will get.

Eventually you'll fall off your diet---everyone does---and you'll end up being fatter and in worse shape than when you started!

When people say they want to "lose weight", what they're really saying is they want to lose unhealthy body fat.

And the only way you're going to permanently do that, my friend, is by eating smaller, healthier, more frequent meals and snacks; getting more rest; reducing stress; drinking more water; and getting up off your lazy butt and exercising.

And though I know you don't want to hear this, losing between one to two pounds per week is realistic and healthy.

Check out: How to lose weight the healthy way and Setting goals for weight loss

NOTE: People who have a lot of excess body fat usually lose more than this when first starting a healthy diet and exercise program---the majority of it being water weight.

And speaking of water, drinking it actually helps---not hinders weight loss. Losing or not, water is good for you. So make sure you drink plenty of it!

Gaining weight is infinitely easier than losing it---just go on the seefood diet. If you see it, eat it!

Oh, if it were only true.

While gaining weight isn't a problem or priority for most, it can be a concern for athletes, people who are naturally thin and anyone else who wants to be bigger, stronger and more muscular.

Gaining or maintaining healthy weight can also be a problem for the elderly and a serious concern for those with eating disorders, chronic and digestive diseases, hormonal imbalances, glandular problems and other medical conditions.

Medical conditions aside, if you take in more calories each day than your body uses you will gain weight. This sounds simple---but putting on healthy weight can be nearly as difficult and frustrating as losing it. In fact, most research shows it actually takes longer to gain healthy weight than it does to lose it!

While putting on good weight may not be easy, there is a solution. And believe it or not, the approach is nearly the same as it is for those trying to shave the pounds off.

In other words, eat more and start building muscle.

How many calories you'll need depends on your age, gender, current weight and activity level. These calories should be in the form of extra meals and snacks and come from a variety of healthy food sources such as low-fat milk and dairy products; eggs, fish, skinless poultry and lean meats; fruits and vegetables; and from whole grain breads, cereals, beans, nuts and seeds.

Also, limit your intake of foods high in calories and low in nutrition. This includes foods with a lot of added sugar like soft drinks, snack cakes, donuts, cookies and candy.

Increasing calories alone will make you gain weight, but extra calories---even good ones---will be stored as fat. You don't want that.

Healthy weight gain comes from building muscle and the only way you're going to do that is through resistance training. That's right boys and girls...you gotta lift weights.

If you want to gain the right kind of weight, this is what it takes!

Healthy Weight Gain and How To Gain Weight

Generally speaking, supplements are powders, potions and pills designed to help accelerate the results you achieve from from your muscle building and weight-loss efforts.

Supplements are just that: sup-ple-ments. They're intended to be used along with healthy diet and exercise programs---not replace them.

But buyer beware: Few products work. Most do not. Some can even be dangerous.

Before wasting your hard-earned cash on any of these mysterious marvels of modern science or turning your body into a pharmacological testing ground, ignore the hype, do your homework and decide if you even need them.

For most, adopting healthier eating habits, exercising on a regular basis and a little patience is all it really takes. And with the exception of a good multivitamin, many people don't take or waste their money on anything else.

The process is almost identical for both and should be done at the same time!

Here's what it takes: