How diet and exercise play a role in weight loss?
Obesity has become an Achilles heel for many. Most obese people realise, often late, that it is extremely difficult to lose and maintain weight. However, medical or surgical intervention cannot be the only answer for the millions of overweight individuals in the world.
The most established long-term strategy for weight loss is by restricting calorie intake popularly known as ‘dieting’. Unfortunately, ‘diet’ is used as a fad most of the times, defeating the real purpose of a well-balanced diet for optimal health.
To understand the relevance of a balanced diet, one needs to understand the principles behind weight changes. It was widely believed, that if calories consumed equals calories spent, then weight can be maintained and in order to lose 2 kg/month, a person generally needs to reduce his/her calorie intake by 500 calories.
In reality, calories are so delicately balanced in the body, that to maintain weight, a person needs to eat exactly the same amount of calories that is spent on a daily basis.
For instance, having 2 potato chips (22 calories) daily, results in 8000 surplus calories over one year. Even this is likely to result in 1 kg of weight gain annually.
This recent understanding has a few major implications on weight loss:
- Restricting 500 calories/day from current intake may be insufficient for weight loss since many people consume 1000-3000 calories extra daily. The correct approach is to calculate one’s daily calories expenditure and then consume at least 500 calories less than the calories spent. This may result in restriction of 500-3,000 calories/ day depending on pre diet food intake and exercise levels.
- One’s diet should not be manipulated for only a few weeks or months with the purpose of weight loss. It should be improved for life. A person’s tendency to gain weight is unchanged over time.
- Once calories through food are restricted, the body starts using internal stores for energy. Initially glycogen (stored in muscles and liver) and then fat depots are used as energy sources. Usually it is advisable that despite dieting, calories intake should always be more than 1000/day to avoid a starvation response by the body.
How the human body resists weight loss?
Reduced food intake results in two major physiological responses
- Increased in ghrelin hormone secretion by the stomach, which makes people feel hungry.
- Reduced food intake over time means that as food digestion decreases, the rate of metabolism will also fall. This means that, with time, people will experience lower levels of weight loss.
Scientifically speaking, exercise on its own does not result in significant weight loss. However, exercises are extremely important to
- enhance diet induced weight loss
- maintain weight in the long-term
- improve fitness and overall health
Enhancing diet induced weight loss
People can increase their daily calorie expenditure by 200-1000 calories through aerobic exercises. If the calorie intake is fixed, calories spent can be increased through exercises and weight loss will thus speed up.
Role in long-term weight maintenance
Regular strength exercises result in increased muscle mass. Muscle cells consume more calories than fat cells. People with more muscle mass burn more calories even at rest. Thus exercise helps people maintain weight long-term.
Improving fitness and overall health
Besides its role in weight loss/maintenance, regular exercises play an extremely important role in one’s fitness through improved cardiac contractility. Aerobic exercises also help improve breathing capacity of a person. They also result in increased glucose utilisation by muscles, thus reducing insulin resistance and improving blood sugar control amongst diabetics.
In conclusion, diet and exercises remains the cornerstone of an attempt to lose weight. The successful outcome is largely based on long-term compliance with the same.
The author is a Senior Metabolic and Bariatric Surgeon, Director, Centre of Bariatric Metabolic Surgery, Wockhardt Hospitals.