Updated: Mar 21
Concept of Weight Loss
In order to have a successful (not to mention efficient) weight loss journey, it is important to understand how our body works. As mentioned in the previous article, our body processed energy surplus and stored as body fat. Hence, in order for weight loss to occur, we will need to incur an energy deficit. Simply put, your total energy expenditure (TEE) needs to be more than the energy from your food intake. Anything that requires energy to perform makes up the energy expenditure. That includes walking, gardening, cleaning, stairs climbing, exercise to sustaining the body’s vital functions (more on this later). When there’s a deficit, the body will then draw on its energy reserves by processing the body fat to usable energy to sustain whatever activity that you are doing, gradually reducing the amount of body fat.
Here’s an example of daily energy deficit:
There are a couple of ways to increase the energy expenditure. It can be done through non-exercise physical activity, exercise or both. Physical activities are basically activities that you do daily, and it can be as simple as commuting to work to grocery shopping. Due to the randomized nature of these activities, it is difficult to quantify the amount of energy required to carry out these tasks. Therefore, a simpler way is to translate the amount of work done into step count. The amount of energy expended for 10,000 steps can range from approximately 250 – 400 kcal, depending on the speed of your movement (12). Although the accuracy of step counting can vary greatly between devices (23), it does provide us with a rough idea of how active we are in a day. A step count of less than 5000 a day indicates a sedentary lifestyle (22). If you find yourself falling into this range, you might want to start moving around more.
Exercise, on the other hand, is a physical activity that is planned and structured for the purpose of improving physical condition. What mode of exercise, how long it will take, how frequent per week, and how intense is it going to be, are all part of the planning. To calculate how much energy that you burned from the exercise, simply choose the specific activity that best describes what you were doing and use the metabolic equivalent of task (MET) value (provided on the Compendium of Physical Activities website), and multiply by your weight (in kg). This works out the amount of energy that you burned per hour. If you only exercise for 30 or 15 minutes, simply divide the energy expended per hour by 2 or 4, respectively.
Although diet does not exactly expend energy like how physical activity and exercise do, it does contribute to the total amount of energy expenditure. Do you know that our body burns calories after we eat? This is because our body requires the extra energy in order to digest the food, and this is known as the thermic effect of food (TEF) (1). The amount of energy required to process protein, carbohydrate and low-fat plant-based diets are higher compared to high-fat food (3, 25). In addition, increased protein intake during weight loss can help to prevent muscle loss (13, 7). Hence, having a good diet can work to our advantage; we just have to be smart with our food choices.
So where do I start?
Before jumping right into a weight loss program, it is recommended to determine your appropriate caloric intake first. Everyone has a minimum amount of energy that is required to sustain the body’s vital functions in the waking state. This is referred to as your Resting Metabolic Rate (RMR). The RMR is the total amount of energy that an individual burns at rest over a period of 24 hours, and it does not take into account your physical activities. Knowing your RMR value allows you to plan and to set realistic energy deficit goal, instead of randomly cutting down on food and exercising. The RMR for women ranges from approximately 1,200 – 1,500 kcal, and the average RMR for men can be between 1,500 – 1,900 kcal (1). To calculate your RMR, you can use one of several different equations such as the one developed by Mifflin for healthy adults (14):
Women: 9.99 × weight + 6.25 × height − 4.92 × age + 5
Men: 9.99 × weight + 6.25 × height − 4.92 × age − 161
(weight in kilograms, height in centimeters, age in years)
Keep in mind that these are just an estimate of your RMR and equations specific to populations are required for a more accurate estimation. If not, a more accurate method would be to undergo a metabolic test using indirect calorimetry. There are many factors that can influence RMR including age, gender, height, weight, fat-free mass, activity level and ethnicity (15, 16, 9). In other words, your RMR can increase or decrease if there are any changes to any of the modifiable factors. For example, increasing your skeletal muscle mass will boost your metabolism slightly (4, 24, 20) due to the fact that muscle cells are metabolically more active than fat cells (15).
However, losing too much and too fast can be harmful to our body (a common example would be crash dieting). Some of the side effects include poor performance, fatigue, lethargy, muscle loss, long term slowing down of metabolism, weight regain, increased risk of dehydration and increased stress on the cardiovascular system (6, 5, 17, 8). Therefore, for the safety of your health, the rate of weight loss should not be more than 1kg per week as recommended by American College of Sports Medicine (ACSM). This is equivalent to approximately an energy deficit of 7,000 kcal per week (1,000 kcal per day).
What would be the best way to lose weight?
So, which is better for weight loss? Is it dieting, exercise, keeping ourselves active daily, a combination of some or all? What mode of exercises should I do then? How hard should I work out? According to a study done by Jung, Hwang, Kim, Park & Lim (2019), there was no significant difference between steady-state exercise and interval exercise in terms of energy consumption during exercise. However, studies have shown that fat oxidation was higher during moderate cardio exercise compared to high-intensity interval training (18, 21). Even though overall energy expenditure may increase as exercise intensity increases, the amount of energy contributed from fat remains the same due to minimal increment in oxygen consumption (19). If the increment in oxygen consumption is minimal, it will not be enough to metabolize fat. Therefore, the increase in energy expenditure is due to an increased in the anaerobic breakdown of carbohydrate and not because of an increased in the breakdown of fat. Compared to resistance training, aerobic training was more effective in reducing body fat (26) and visceral fat (10) in overweight and obese adults.
Nevertheless, this is not to say that we should only do aerobic exercises. Resistance training helps to maintain muscle mass during weight loss, especially for older adults (2) and as mentioned earlier, this helps to maintain/increase your energy expenditure throughout the day. Moreover, having a variety of exercises (resistance training, interval training, circuit training etc.) in the program would help with training monotony, and for those who have limited exercise duration due to time constraints, interval training helps to address these issues (typically done within 30 minutes due to the nature of the exercise). Having said that, as interval training is generally performed at a high-intensity level, this sort of training is only appropriate for those who can perform such exercises.
When it comes to weight loss, there isn’t a program that is more superior than the other. More importantly, you should consider whether it is practical and sustainable for you. For someone who holds a desk job, it might be difficult for him or her to be constantly on their feet, and so, it might be more practical for them to focus more on their diet and exercise. For those who are obese, it might better for them to improve on their diet and lifestyle first before introducing exercise to their program gradually. That way, it can help them to cope better with lifestyle changes that they can sustain in the long run. For those who find themselves reaching a plateau, they might benefit from a periodized program where the training goal for one phase emphasizes on improving muscles mass while minimizing fat gain before focusing on increasing energy expenditure while maintaining the muscular mass in another phase.
Regardless of the approach, having a better understanding of how our body functions, along with consistent effort and discipline, would certainly help with some level of success in managing our weight. So, start moving and find what works best for you!
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