With all the fuss about weight gain and obesity, the question in most people’s lips is how much should we be eating? If you are worried you’re eating too much – or too little, read on to find out how to calculate your calorie needs.
Most nutrition guidelines suggest an intake of 2,000 calories for women and 2,500 for men per day, but experts say these figures may not be accurate today because of changing lifestyles and eating habits. Many people are today less active yet they continue to consume similar calories as people who walk everywhere, till the shamba, fetch water and firewood and housework. They may also eat more natural and less dense calorific foods.
Experts recommend that if activity levels drop we need to reduce our energy intake to maintain our weight. A study by the World Health Organisation estimates that an inactive woman of average weight would need to eat 1,932 calories a day – or increase calorie expenditure through exercise to have a healthy weight.
The good news for people who exercise regularly is that it allows them to consume more calories and still maintain their weight. Every bit of activity adds to your daily calorie expenditure. If you don’t want to lose weight, snack regularly on healthy snacks, such as fruit or vegetables to maintain energy balance. Exercise lowers your body fat and replaces it with lean tissue and muscle, both of which are more metabolically efficient than fat.
Working out your calorie needs…
First you need to calculate your Basal Metabolic Rate (BMR), which is the number of calories you need just to stay alive including those burned for essential functions such as heart rate, brain activity and breathing.
Here is how you do it:
For men: (13.75 x w) + (5.0 x h) – 6.76 x a) + 66
For women: (9.56 x w) + (1.85 x h) – (4.68 x a) + 655
(Abbreviations: w=weight in kg, h=height in cm, and a=age)
So, for example, if you are a 35-year-old woman who weighs 65kg and is 168cm tall, your BMR will be: (9.56 x 65) + (1.85 x 168) – (4.68 x 35) + 655 = 1,751 calories. To that BMR figure you need to add the calories you expend exercising. According to experts, your daily energy requirements are somewhere in the order of 1.4 x your BMR figure if you do some exercise, or 1.2 x BMR if you are usually quite inactive.
Once your BMR has been calculated, it’s very easy to determine how much (or little) you need to eat to lose or maintain weight. Any activity over and above this basal, or resting state – such as digesting food, ingesting stimulants such as caffeine, experiencing emotions such as stress or happiness, or general activity – increases your metabolic rate. Regular exercise is particularly helpful in boosting metabolism.
It is estimated that the increased lean body mass, or muscle from working out can raise total daily energy expenditure by between eight per cent (about 143 calories per day) for a moderately active person. Muscles burns 50 calories per pound, compared with the partly three calories required by fat. This explains why athletes and people who exercise regularly use calories more efficiently.
Eating regular, healthy meals can also boost metabolism, which is why dieters who severely restrict their food intake often complain their metabolism is sluggish. Extra energy is burned after eating due to the increased activity of the digestive enzymes and faster blood flow. Age also influences your metabolic rate.
Some body tissues use up energy at a faster rate than others; the brain and liver, for instance, require more energy at rest than muscle. Fatty tissue requires the least. The ratio of internal organs to muscle and fat determines how much energy is used per pound of someone’s body weight. Children have faster metabolic rate because their proportion of internal organs to body fat is higher. Generally, metabolism slows as we get older. This happens as your proportion of fat rises and your muscle mass falls, both of which are a result of lower levels of physical activity.
When you eat too little…
The prospect of losing weight may seem appealing but people who eat too little and work out too excessively are putting their long-term health at risk. Calories are needed for the body to function optimally; without them, things start to break down. Many under-eaters and over-exercisers experience iron-deficiency anaemia and poor circulation, and women can get exercise amenorrhea, which causes their periods to stop.
When this happens, it is a warning sign that levels of the hormone oestrogen have plummeted to those of a postmenopausal woman. Since oestrogen is vital for the normal development of bone it can mean an underweight woman may start losing bone mass instead of building it, putting her at risk of osteoporosis.
Getting it right…
People often get totally confused when it comes to working out how many calories they need to cut out in order to lose weight. Weight control comes down to creating a calorie budget as weight loss occurs when you burn more calories than you eat. So, if you need 2,400 calories a day to maintain your weight but eat only 2,000, you will lose weight. The kinds of calories you eat are less important. If you choose to consume 300 of your daily 2,000 calories from chocolate, you will still lose weight, though you may not be getting enough nutrients.
Experts recommend you subtract 20 per cent of your total daily calorie requirement to achieve weight loss. If you need 2,200, then subtract 440 calories and the weight will drop steadily. One big mistake is to cut calories too drastically. If you do that you will lose muscle, slow your metabolism, eat too few of the nutrients you need to stay healthy and the chances are you will regain weight lost quite quickly.
Published in December 2014