Diet Information
What Determines Our Body Weight and Fat

Factors That Influence Weight

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What Determines Our Body Weight?

Our weight is typically influenced by a variety of factors, including age and gender. Here are four of the most important body weight predictors.

Weight Factors We Can Control

- How Many Food Calories We Consume
- How Many Exercise Calories We Burn

Weight Factors We Cannot Really Control

- Our Basal Metabolic Rate (BMR), our metabolic 'tickover' speed.
- Our Rate of Dietary Thermogenesis

Food-Calorie Intake

The number of calories we eat is a decisive factor in whether we are underweight, normal weight, overweight or obese. How nutritious those calories are can also affect our weight. The less nutrition in our daily diet, the less healthy we are and (eg) the less efficient our body is in metabolizing food into energy or fat-storage. Several metabolic disorders (eg. insulin resistance) are associated with excess weight and unhealthy diets.

Exercise-Calorie Expenditure

The fewer calories we burn in physical exercise, the greater our chances of building up a calorie surplus to be stored as body fat. Obesity experts consider lack of exercise to be a major underlying cause of high obesity levels. For example, 30 minutes of brisk walking each day burns 73,000 calories a year. The equivalent of 20 pounds of body fat.

Our Basal Metabolic Rate (BMR)

Basal or resting metabolic Rate is our body's 'tick-over' speed - the rate at which it uses up calories to maintain essential functions (eg. heart beating, lung movement, body temperature control etc.) while at rest. On average, BMR utilizes about 60 percent of our calorie-intake. BMR is genetically inherited and varies from person to person. People with a lower BMR are more at risk of becoming overweight than those with a higher BMR.

BMR rises in response to increased physical exercise. This rise is typically maintained for up to several hours after activity has ended. An optimum weight loss exercise program combines aerobic and weight-training exercise. Aerobic activity to burn calories and raise metabolic rate in the short term; weight-training to increase muscle-mass and raise metabolism long term.

Basal metabolic rate is directly influenced by hormones (eg. thyroid hormone) as well as a number of other biochemical processes, many of which are genetically inherited.

Thermogenesis

Thermogenesis, sometimes referred to a dietary thermogenesis) is the body's ability to burn excess calories as heat. Thermogenesis is part of our genetic inheritance and varies from person to person. It occurs partly in response to eating food and its rate may depend on the type of food eaten. Thermogenesis typically accounts for about 10 percent of calories burned. itself burns off.

What Else Determines Body Weight?

Age and gender also affect our weight and body fat.

Age
Typically, the older we get, the less muscle mass we have, due to under-use. Since more calories are required to maintain muscle-tissue than fat-tissue, we tend to gain weight in middle age and in later life.

Gender
Gender is also important, as women tend to have more fat cells and a higher body fat percentage than men. Also, men typically store body fat around the middle (apple-shape), while pre-menopause women tend to store fat around the pelvis, buttocks and thighs (pear-shape). Fat storage among postmenopausal women whose estrogen levels fall, is more similar to fat storage among males. Note that excess fat around the middle (abdominal obesity) is now regarded as an independent risk factor for cardiovascular disease as well as metabolic disorders like insulin resistance and type 2 diabetes.

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