The secret to packing on pounds of solid muscle mass is simple: For the most part, the types of foods you eat on a muscle-gaining program are the same ones you should eat all the time, whether you want to lose, gain or maintain - you just need to eat more of them. "Just eat more" is easier said than done, however. It seems like you're constantly shopping, cooking and eating. Sometimes preparing food and eating it can seem like a full time job! One way to make gaining weight and forcing down all that food less of a chore is to choose foods (or supplements) with a HIGHER CALORIE DENSITY. By doing so, you can get more calories in the same amount of food.

All proteins and all carbohydrates have 4 calories per gram and all fats have 9 calories per gram, but not all foods have the same number of calories per unit of volume. Let me explain:

Imagine for a moment, two measuring cups (the kind you have in your kitchen) and notice the amount of space in each container. Got it? Now visualize the two cups side by side; one filled with chopped cucumber and one filled with raisins. Each cup now contains exactly the same VOLUME of food, right? But did you know that the cup of raisins has 37 times more calories? That's right! The cup of cucumbers contains 14 calories, while the cup of raisins contains 520 calories. If cucumbers and raisins both have four calories per gram, then how could this be? The answer has to do with calorie density. The cucumbers have a lower calorie density because they have a higher fiber and water content. The calories in the raisins are more "concentrated."

And that's the secret to getting enough calories to gain weight: choose calorie-concentrated foods.

If you learn which foods are nutrition dense and calorie dense, you can use this information to help you gain lean weight more easily than ever before.

Fibrous carbohydrates and vegetables such as lettuce, asparagus, cucumber and broccoli have very low calorie densities because your body can't absorb the caloric content of fiber. That makes veggies an excellent choice when you want to lose body fat. Before competitions, bodybuilders usually reduce or remove high calorie simple sugars and starches from their diets and replace them with fibrous carbohydrates. (Goodbye bagels and pasta, hello broccoli and asparagus!)

On the other side of the coin, the low calorie density of most vegetables is the very reason that they don't help you gain weight. Think about it; you would have to eat a wheelbarrow full of lettuce, cucumbers or spinach before you consumed enough calories to make the scale budge at all! It's wise to always include vegetables in your diet (because they're good for you), but you won't get enough calories to gain weight from veggies alone; you have to eat lots of high density foods or you'll be fighting an uphill battle.

So now let's look at some "calorie-dense" foods that can help you pack on the pounds:

Simple carbohydrates such as fruit have higher calorie densities than vegetables because simple carbs are more concentrated and have less fiber. Fruit juice is even more concentrated than the fruit itself. A medium sized orange contains about 60 calories. A glass of orange juice has about 160 calories. Fruit and fruit juice, therefore, make great additions to a weight-gaining program.

Taken to the extreme, concentrating and refining carbohydrates results in empty calorie products like white sugar and white bread. Although these are calorie dense foods, they have little or no nutritional value. Don't add nutritionally void foods to your diet just for the sake of more calories - it's the quality and nutritional value of the calories you want, not just the quantity. You should look for foods that are high in calories that are unrefined and as close to their natural form as possible (the way they came out of the ground).

Complex carbohydrates (starches) such as whole grains, pasta, cereals, beans, yams, potatoes and rice also have higher calorie densities than fibrous carbs. A typical restaurant sized serving of pasta contains 800-1000 calories. Obviously, pasta and other complex carbohydrates are great foods for gaining weight.

Ok, now that you know what carbs to eat, let's talk about fat. Fat can also have a major impact on the calorie content of foods. Fats have more than twice as many calories per gram than carbohydrates or protein (9 calories per gram vs. 4 calories per gram), so foods that are 100% fat have the most calories per volume. Olive oil, which is pure fat, contains 1920 calories per cup. Any food that has a lot of fat in it will have a high calorie density. Peanut butter, for example, has 1600 calories per cup; Cashews have 780 calories per cup.

I'm not suggesting that you start devouring French fries, cheeseburgers and sausage every day for the sake of gaining weight - if you do, you'll gain weight all right - right on your belly or backside! Your diet should always be low in fat (15-25% of your total calories), but not all fats are bad. It's the saturated fats like fried foods, butter and tropical oils that you should avoid.

In small amounts, unsaturated, "healthy" fats are not only good for you, but they can help you gain weight more quickly than if you didn't eat any fat at all. Just one tablespoon of flaxseed oil and two tablespoons of peanut butter would add nearly 500 calories to your daily diet and you'd hardly notice that any extra food was added.

Protein foods that contain some fat will also be higher in calories. 4 oz of Chinook salmon has 262 calories and 15 grams of (good) fat; 4 oz of Haddock has 137 calories and only 1 gram of fat. Because of the higher calories and the essential fatty acids (good fats), cold water fish like Salmon are another great addition to a weight gain program.

The best proteins for gaining muscle are the lean ones like chicken, lean beef, egg whites, turkey and fish. Lean cuts of red meat like round or flank steak are excellent for gaining weight. Avoid fatty cuts of beef, as well as pork, sausage, bacon and whole milk products because they contain large amounts of artery-clogging, unhealthy saturated fat.

I'm a huge believer in always choosing whole foods over supplements whenever possible. However, it's not easy to eat whole foods 5 or 6 times per day if you have a busy schedule. If you have a hard time getting enough calories from food, then you should consider using a weight gain or meal replacement product because drinking your calories is a lot easier than eating them.

Meal replacements are usually powdered products that you mix with water, milk or juice. You can also increase the calories further by adding peanut butter, flax oil, fruit or your other favorite ingredient and mixing up the whole concoction in a blender.

Don't just blindly follow the instructions on the container. One thing that most people don't realize is that you need to customize your supplement intake to your exact calorie needs. Just because the package says there are "1000 calories per serving" doesn't mean that's how many you need. Adjust the serving size to fit your own diet.

For example, if you need 3000 calories to gain weight, that breaks down into five 600-calorie meals or six 500-calorie meals. There's no need to shovel down 1000 calories at a time just because the label says so - that's only going to make you fat.

Some products were designed as meal replacements for fat loss programs. These usually come in individual serving packets, they have about 280-300 calories per serving and they contain more protein than carbohydrates; this way, they fit into the guidelines of a low carbohydrate, high protein, fat burning diet. These products are not as cost-effective when you're trying to gain weight. 300 calories is not enough for mass-building meal. If you decide to use this type of product for weight gain, you'll need to mix it with a calorie containing liquid like juice or skim milk to bring the calories up to 500-700 (or whatever your diet calls for).

When you want to gain muscle, you'd be better off choosing a product that was specifically designed for that purpose. These "weight gainers" are much more concentrated in calories and contain more carbohydrates.

Using mostly carbs (sugars) and skimping on the protein is a dirty trick that supplement companies use to make a product cheap to manufacture. Read the labels carefully and avoid any product that is mostly sugar with very little protein. A good product will have approximately one part protein for every two parts of carbohydrates and small amounts of fat. For example, a drink mix with 40 grams of protein, 80 grams of carbs, and 2 grams of fat would provide almost 500 calories. If you wanted even more calories, you could mix the powder in skim milk or juice instead of water.

So, let's summarize your strategy for quickly and easily adding more calories to your diet:

1. Continue to eat the same healthy foods you always eat, but simply eat more of them.

2. Choose foods with a higher calorie density. You could eat broccoli and salad until your face hurts from chewing so much, but you still won't get enough calories.

3. Eat plenty of starchy carbohydrates including whole grains & cereals, pasta, potatoes, yams, beans, rice and oatmeal.

4. Don't be afraid of adding a little bit of fat. Keep your diet low in fat overall, but add in some of the healthy "good" fats (such as flax oil, olive oil, or a couple tablespoons of peanut butter) and you'll gain weight more quickly.

5. Just because you're trying to gain weight doesn't mean you have a license to eat anything you want. Go for nutritional value as well as calorie density; avoid saturated fats, sugar and processed junk foods.

6. If you can't seem to get enough calories from food, then a meal replacement or weight gainer supplement can make your life a lot easier. Adjust the serving size to fit your calorie needs and make sure the product has a good protein to carb ratio.

7. Don't be afraid to drink a lot of your calories in the form of low fat/skim milk, juice or supplements/shakes.

Well, that's it! Follow these strategies diligently and you'll gain pounds solid muscular weight more easily than you ever have before without having to chain yourself to the refrigerator!

You can learn much more about calories, metabolism, and muscle growth by visiting Burn the Fat, Feed the Muscle!