The body is a very complex machine, but its laws are pretty simple when it comes to weight loss and weight gain. You pretty much consume food to help provide you energy and help your body function. If you consume more than your body needs, it converts it into fat and stores it for a rainy day. This leads to "weight gain".
I put "weight gain" in quotes because your weight on the scale is not always the greatest determinant of your health. Weight gain can be as a result of fat, but it can also be as a result of muscle. But this is a discussion for another day.
Now, some people naturally have higher metabolisms, which means they burn more energy doing the same activities as others. This is one of the major reasons why some folks are naturally slimmer, even though they consume the same foods. You can increase your metabolism through regular exercise.
I have heard friends tell me they eat as much as they want of particular foods because they are "healthy", and I believe this is a common misconception. Think about it this way: Almost everything you eat has calories. Your body needs these calories to function. However, even if something is healthier and has fewer calories than some other food, it still has calories.
Let's use an example. A medium sized apple has about 90 calories. A fried chicken thigh from KFC contains about 250 calories. Obviously, if you eat 4 pieces of fried chicken, you are far along in your calorie count for the entire day, and it is equivalent to about 11 apples.
While that sounds fabulous for an apple lover, it still highlights one thing: You cannot simply eat 50 apples throughout the day and think your weight will be unaffected. Even apples have calories too, and so you have to make sure how many your are eating is consistent with how much you are burning. These are 2 extreme examples, so you can imagine how much closer it gets with food that falls somewhere in between.
I hope that helps you are you work though those fitness resolutions!
Cheers Eights & Weights!
Photo credit: BusinessWeek.com