Your body is an amazing machine that is able to extract energy from just about anything you eat. While glucose is your body's preferred energy source, you can't convert fat into glucose for energy; instead, fatty acids or ketones are used to supply your body with energy from fat.

Juice is typically sold in concentrate form to increase its shelf life and to reduce its shipping weight when sent from fruit-producing regions and countries to your local supermarket.

Fatigue and your weight are tightly intertwined. Being overweight means you have to work harder to do simple physical tasks, such as climbing the stairs and walking from the bus stop. A large body size may also interfere with nightly sleep as it increases the chances that you suffer from sleep apnea.

Fat-free mass, also known as lean body mass, refers to all of your body components except fat. It includes your body's water, bone, organs and muscle content. However, when it comes to weight management and body composition, fat-free mass refers primarily to muscle mass.

It's a well-established "rule" that frequent meals boost your metabolism and prompt weight loss, but research doesn't necessarily back this rule up. While this eating pattern helps some people, it isn't absolutely necessary for healthy weight management.

The soleus and the gastrocnemius are the two muscles that make up the calf. Without these versatile muscles you would not be able to drive a car, walk or lift your toes. Yet calves can be a source of body image distress: too small, too big or even too muscular.

Influenced by what he sees on TV and in magazines, your teen may worry that he's not thin enough. Some teens take longer to grow into their adult height than others and may continue to harbor some of that "baby fat."

When you’re in your 30s, your basal metabolism begins to drop. From this age on, the average adult will gain a pound a year. Here's what you need to know.

Your ideal body weight is largely based on your height. Even petite women can use their height to determine their ideal body weight. However, it's also established by your body frame, which falls into one of three categories: small, medium and large.

There isn't one ideal body weight for all men of the same height, since body composition plays a role. Muscle weighs more than fat, so a muscular guy could weigh more than a man of the same height who carries much of his weight as fat.

You may wear a small size and look slender to your friends, but underneath those petite clothes, you're lacking muscle and holding a large amount of fat. The condition, colloquially known as "skinny fat," or, in medical literature, as "normal weight obesity," can have serious health implications.

Although body mass index and body fat percentage tend to be related, BMI -- a calculation based on height and weight -- doesn't necessarily accurately predict a person's body fat percentage.