Energy needs for body’s basic functions stay fairly consistent and aren’t easily changed. Basal metabolic rate accounts for about 70 percent of the calories we burn every day. In addition to your basal metabolic rate, two other factors determine how many calories your body burns each day.
Food processing (Thermogenesis) – Digesting, absorbing, transporting and storing the food you consume also takes calories. This accounts for 100 to 800 of the calories used each day.
Physical activity – Physical activity and exercise — such as playing a sport, jogging or walking, climbing up stairs or any physical activity account for the rest of the calories your body burns up each day. Physical activity is by far the most variable of the factors that determine how many calories you burn each day.
These are the modifiable factors and are impacted by our attitude towards health and fitness. Conscious actions towards adapting healthy diet and lifestyle can help increase energy expenditure.
Metabolism and weight
It may be tempting to blame metabolism for weight gain. But because metabolism is a natural process, our body has many mechanisms that regulate it to meet your individual needs. Only in rare cases do we see excessive weight gain from a medical problem that slows metabolism, such as Cushing’s syndrome or having an underactive thyroid gland (hypothyroidism).
Unfortunately, weight gain is complicated. It is likely a combination of genetic makeup, hormonal controls, diet composition and the impact of environment on our lifestyle, including sleep, physical activity and stress. All of these factors result in an imbalance in the energy equation. We gain weight when you eat more calories than you burn — or burn fewer calories than we eat.
While it is true that some people seem to be able to lose weight more quickly and more easily than others, everyone will lose weight when they burn up more calories than they eat. Therefore, to lose weight, we need to create an energy deficit by eating fewer calories or increasing the number of calories we burn through physical activity or both.
The human body is designed to save excess energy for times when food may not be available, so the extra energy is stored as fat. If we take in fewer calories than our body needs to perform all of its functions, it will be forced to break down stored fat for energy and we will lose fat.
However, our body also breaks down muscle. Remember, muscle is the biggest contributor to our metabolic rate, so losing muscle means our calorie needs decrease. We can offset this decrease in metabolic rate by doing strength training as part of our exercise routine, to help maintain our muscle mass.
People trying to lose weight are usually advised to create a calorie deficit of 500-1000 calories per day.
This means eating 500-1000 calories less than what we need to maintain our weight. This can be achieved either through eating 500-1000 fewer calories, by exercising enough to burn that many calories, or by a combination of the two.
For example, stop eating afternoon snack of a 300 calorie samosas and burn off 200 calories running.
- A 500 calorie deficit (or excess) per day, over 7 days, will add up to 3500 calories. This is equivalent to half a kg / one pound of fat lost (or gained) in a week.
- A 1000 calorie deficit (or excess) per day will add up to 1kg /2 pounds lost (or gained) in a week.
However, creating such a large deficit every day may be difficult and counterproductive. Remember that cutting calories too quickly and/or too much will slow your metabolic rate.
The American College of Sports Medicine warns that calorie levels should never drop below 1200 calories/day for women or 1800/day for men; even these levels are very low.
There’s no easy way to lose weight. The foundation for weight loss continues to be based on physical activity and diet. Take in fewer calories than you burn, and you lose weight. Our knowledge is increasing about all of the mechanisms that impact appetite, food selection, and how your body processes and burns food.
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