Register
Sign in17 October 2009
Metabolism and Basal Metabolic Rate (BMR)
Bookmark this page:
Metabolism: What exactly is it?
Metabolism is described as the physical and chemical processes by which substances are produced or transformed (broken down) into energy or products for the uses of the body. To relate this to calories, your metabolic rate is the rate at which your body uses energy, or, in other words, burns calories.
Metabolism is a crucial bodily function as it enables the body to turn the food and internal energy sources that it has into useable energy to keep organs and bodily functions working.
The body's metabolism is most affected by nutrition, hydration and physical activity. For optimum metabolic heath, all of these factors need to be considered - if any of these is lacking, this can lead directly to a decrease in the body's metabolic rate.
Needless to say, as you will find out below, weight loss and weight maintenance are directly related to healthy metabolism.
Metabolic rate and weight loss
Your metabolism is working all the time whether you're sitting around or running on treadmill converting food and / or body fat in the body into useable energy products to keep you alive.
It is probably of no surprise that your metabolism slows down during periods of inactivity and speeds up during periods of exertion.
Your Basal Metabolic Rate (BMR) is the number of calories you would burn if you remained completely inactive - i.e. you did nothing but sleep all day. You might wonder why calories are burned when you are in such a state but when you think about it, your body still requires energy to perform bodily functions such as respiration, the pumping of blood around the body, and maintenance of body temperature.
The faster your BMR, the more calories you burn and vice-versa. You might hear people who are naturally skinny saying that they have a fast metabolism so can eat anything and everything that they want without putting on any weight - there is an element of truth in this as you'll see below
- Genetics - it is true that some people are born with faster metabolisms than others;
- Age - BMR reduces with age. A good rule of thumb is that after you reach 20 year of age, it drops about 2% every 10 years. This is because from your early 20's onwards, studies have shown that the average person gains 1lb of body weight per year yet loses 1/3lb to 1/2lb of muscle. As you will find out below, the less muscle you have, the lower your BMR;
- Gender - men, in general, have a greater body muscle mass percentage and a lower body fat percentage than women resulting in them having a higher BMR;
- Weight - the more you weigh, the higher your BMR;
- Body Surface Area - the greater your body surface-area factor, the higher your BMR. Tall, skinny people have higher BMRs than shorter people of equal weight. If both consume the same number of calories per day over a year, the shorter person will gain more weight than the taller person;
- Body Fat Percentage - the lower your body fat percentage, the higher your BMR. The lower body fat percentage in the male body is one reason why men generally have a 10-15% faster BMR than women;
- Diet - starvation or serious abrupt calorie-reduction can dramatically reduce BMR by up to 30%. This is a natural bodily reaction to conserve energy whilst your body thinks that you are in 'starvation mode'. If you are dieting, reduce your calorie intake slowly and stimulate your metabolism increase your activity levels to counter this. If you don't get the balance right, although you might be consuming less calories, your body will burn fewer calories and you'll find it hard to lose weight; The message therefore is that is that dieting alone will not be as effective a combination of increased exercise and dieting. The negative effect of dieting on BMR can be offset with a positive effect from increased exercise;
- Exercise and Muscle - physical exercise is important when trying to lose weight as it stimulates your metabolism and leads to increased calorie expenditure in the short-term. Exercising, however, also helps raise your BMR in the long-term through the formation of extra muscle tissue which is more metabolically demanding than fat tissue;
- Stress - high levels of stress hormones in the body will often result in an increase in BMR.
Calculating your Basal Metabolic Rate (BMR) and daily calorie requirement
Before you even begin any dieting and exercise plan, you need to set some goals against some reference points.
No doubt, you main goal is your target weight. This can only be reached by adjusting your calorie intake and activity levels so that your calorie expenditure is greater than your calorie consumption. Making such adjustments is meaningless, however, if you don't know how many calories you already burn in a day as without this information, you will not know whether your new regime will cause you to lose or maintain weight!
Thus, the very first stage is to calculate how many calories you actually burn in a day - your total daily energy expenditure (TDEE).
TDEE is the total number of calories that your body expends in 24 hours, including all your normal activities. TDEE is also known as your 'maintenance level'. Knowing your maintenance level will give you a starting reference point from which to begin your diet and exercise regime.
Methods of determining calorie needs
There are many different formulae you can use to determine your calorie maintenance level by taking into account the factors of age, sex, height, weight, lean body mass, and activity level.
The Purple Weight Loss calculator is based on the Harris-Benedict formula which takes account of height, weight, age, and sex to determine your basal metabolic rate (BMR) and flexes the result depending on your daily activity levels. This will prove very useful to you in helping you to finding your reference point for starting your new health drive. To find out your BMR, just register with Purple Weight Loss for free today!