Fat is known to have two main purposes:
1) Fat stores excess calories in a safe way so you can use them when you're hungry, and
2) Fat releases hormones that control metabolism.

The truth is that overweight women have higher levels of male hormones, which increases their risk of heart disease. Those hormones also cause male pattern balding, some excess facial hair, and acne. More truth? Overweight people often suffer from sleep disorders such as sleep apnea, which is dangerous. Sleep apnea causes breathing to stop many times during the night. This makes oxygen levels drop, which affects the heart and increases risk of heart attack, stroke and diabetes. But relax; a certain amount of body fat is necessary for storing energy, heat insulation, shock absorption, and other functions.

Obesity is an excess proportion of total body fat. A person is considered obese when his or her weight is 20% or more above normal weight. The most common measure of obesity is the body mass index, or BMI. A person is considered overweight if his or her BMI is between 25 and 29.9; a person is considered obese if his or her BMI is over 30. BMI is calculated by dividing your weight in kilos by your height in meters squared, or by multiplying your weight in pounds by 703, then dividing by your height in inches squared.

The number of calories you need each day varies depending on your body size and activity levels. Someone who needs about 2,000 calories a day should eat no more than 65 grams of fat a day on average. To determine your ideal daily dietary fat intake:

1. Take the number of calories you eat each day and multiply it by 30 percent (.30). For example: 2,000 calories x .30 = 600 calories from fat.

2. Divide your answer by 9 because there are 9 calories in each gram of fat. This will give you the number of grams of fat per day that should be your upper limit goal. Here, it's: 600 / 9 = 65 grams.

A person who gets 2,000 calories per day ideally should not consume more than 65 grams of fat. Some researchers suggest that even 65 grams of fat in a 2,000 calorie diet is still too much fat.

Abdominal, or belly, fat is viewed as a bigger health risk than hip or thigh fat. It has a worse effect on insulin resistance, boosting the risk of diabetes,  and a worse effect on the level of fats in the blood,  boosting heart and stroke risks. Belly fat, or an apple-shaped body, is also most associated with heart disease and other diseases, such as metabolic syndrome and type 2 diabetes. The bigger your waist, the higher your risk of developing heart failure, a condition where the heart isn’t pumping enough blood out and fluid begins to back up into the lungs and/or pool in the feet and legs.

Brown adipose tissue (or brown fat) is a rapid source of energy for infants and forms about 5% of their body weight. It is brown because the cells in it are packed full of small cellular organs called mitochondria, which are energy factories, and it has a rich supply of blood vessels. Brown fat is virtually gone by adulthood.

The normal amount of body fat (expressed as a percentage of body weight) is between 25%-30% in women and 18%-23% in men. Women with over 30% body fat and men with over 23% body fat are considered obese.

There are 3,500 calories in a pound of fat. You need to burn off 3,500 calories more than you take in to lose 1 pound. This translates into 500 calories per day to lose 1 pound in a week, or 1,000 calories per day to lose 2 pounds in a week. (1-2 pounds per week is generally considered to be a safe rate of weight loss). This can be achieved by eating fewer calories or using up more through physical activity. A combination of both is best.

Believe it or not, healthy skin and hair are maintained by fat. Fat helps the body absorb and move the vitamins A, D, E, and K through the bloodstream.

Being obese means having so much body fat that your health may be in danger. If you are obese, you are more likely to develop type 2 diabetes, high blood pressure, high cholesterol and triglycerides, coronary artery disease (CAD), stroke, and sleep apnea, among other conditions. If you lose weight, your risk for these conditions is reduced. Where you carry body fat is important. If fat builds up mostly around your stomach (sometimes called apple-shaped), you are at greater risk for type 2 diabetes, high blood pressure, high cholesterol, and coronary artery disease than people who are lean or people with fat around the hips (sometimes called pear-shaped).

Hyperlipidemia describes high fat content in the blood. High blood cholesterol that runs in families, called familial hypercholesterolemia,  is the most common inherited type of hyperlipidemia. It predisposes those who have it to premature hardening of the arteries  including coronary artery disease with heart attacks at an unusually young age. About half of men and a third of women with these conditions suffer a heart attack by age 60.

During this process called hydrogenation, hydrogen is added to vegetable oil. Hydrogenation turns a liquid fat such as vegetable oil into a semi-solid (harder), more shelf-stable fat, such as margarine. Most oils are only partially hydrogenated, which creates harmful trans fats that can raise cholesterol.

Food manufacturers add hydrogen to vegetable oil to increase the shelf life and flavor stability of foods. Flavor stability means that the processed food will keep its intended flavor for longer periods of time. Partially hydrogenated oils are popular in processed foods because they are cheap, stable, and widely available.

Your metabolism involves a complex network of hormones and enzymes that convert food into fuel. These enzymes and hormones also affect how efficiently you burn that fuel. Metabolism also describes the entire range of biochemical processes that occur within us (or any living organism). These processes involve both the buildup and breakdown of substances.

Surprised? It's true; the more weight you carry, the faster your metabolism is likely running. "The simple fact is that the extra weight causes your body to work harder just to sustain itself at rest, so in most instances, the metabolism is always running a bit faster," says Molly Kimball, RD, sports and lifestyle nutritionist at the Oscher's Clinic's Elmwood Fitness Center. That's one reason it's almost always easier to lose weight at the start of a diet and harder later on. Kimball says: "When you are very overweight, your metabolism is already running so high that any small cut in calories will result in an immediate loss."