Have you ever wondered what happens to all those calories you eat? How come two people can eat the same amount of food and yet, the first one is overweight while the second one remains skinny? By understanding how our bodies burn the calories we eat from food, we can be more successful at our weight management goals, whether they be maintaining, losing or gaining weight. Thermogenesis Thermogenesis literally means "the origin of heat". It refers to the calories burned or heat generated by the body. There are several types of thermogenesis or calorie-burning conditions that occur on a daily basis. These are basal, exercise-induced, diet-induced, and adaptive thermogenesis. These factors may account for why certain people tend to stay lean, while others are prone to being overweight.
It is also called "basal metabolic rate" (BMR) or "resting metabolic rate" (RMR). It is the minimum amount of calories your body requires to support itself. These are the calories your body needs to keep breathing, to keep your heart beating, and to maintain cellular processes of your different body organs - the stuff that keeps you alive.
Basal metabolic rate is primarily influenced by the amount of lean body mass (what percentage of your body weight is lean or not made up of fat cells), especially muscle.
Two men of the same age, height and weight may have different basal metabolic rates because the first man is 80 percent lean and 20 percent fat while the second man is 88 percent lean and 12 percent fat. Because the latter has more lean body mass, which is more metabolically active than fat, he will have a greater BMR. This just shows that weight isn't everything. Body composition is more important.
Scientists estimate that BMR accounts for 60 percent of the total calories burned by your body everyday! It is the single largest component of energy expenditure. It is not that easy to "reset" your metabolic rate but there are ways to increase your lean body mass and thus, increase your BMR slightly.
One of those ways is to strength train or lift weights. Even a variance of 50 to 100 calories a day will have a significant influence on your long-term ability to control your weight. A case in point is the experience of not being able to burn calories as fast as you used to when you were younger. Muscle atrophy due to leading a sedentary lifestyle plays a big role in the decline of BMR after the mid-20s.
This means the number of calories burned during physical activity. In the average person, EIT or exercise-induced thermogenesis accounts for 10 to 30 percent of the total calories burned daily. The exact amount depends on the frequency, intensity, and duration of the exercise. The more often, the harder, and the longer you exercise, the more calories you burn. Exercise can be aerobic (swimming, walking, cycling, etc.) or anaerobic (weight lifting or short bouts of aerobic type movement done at near-maximum effort).
Many people seem to think that only formal exercise sessions burn calories. Just as important, and often overlooked as a source of calorie burning, are "activities of daily living" (ADL). The number of calories burned varies tremendously among individuals depending on how active or sedentary their daily routine is. For example, many sales people gain weight once they are given desk-bound jobs.
ADL has the potential to burn a significant amount of calories. It all depends on a person's lifestyle habits. Some people seem to go out of their way to avoid any unnecessary physical movement. These individuals fight for the closest parking space on their way to their killer aerobic class. Or the people who seem to be walking "under the moonlight" on their way to work. On the other extreme are the people who seem to be constantly on the move. They don't just walk as they shop, they race. PIf you are a laid back sort of person, you can burn more calories if you purposely plan to become more physically active throughout the day. Here are some examples you can put into action. If your office is on the third floor, take the stairs instead of the elevator. Park your car at the farthest part of the parking lot. If you are taking public transportation, get dropped one or two blocks away from your destination. Walk up the escalator instead of just standing there.
Even if the amount of calories you burn from all these strategies is relatively small, say approximately 100 calories a day, you could lose about one pound of fat in a month (3,500 calories equals a pound of fat). Keeping physically active the whole day is, perhaps, the most practical piece of advice that weight management experts can give us. As one leading weight control authority put it, "if you want to remain slim all your life, just get off your butt"!
It is sometime also called "specific dynamic action" or SDA. It is the amount of calories your body burns when digesting, absorbing and metabolizing a meal. In other words, it takes calories to use the calories in food. SDA constitutes about 10 percent of the total calories burned.
The kind of food you eat affects SDA. Protein elicits the highest SDA, followed closely by carbohydrates. Fat uses up a significantly smaller amount of SDA to be digested. This is one of the reasons that a high-fat diet can be detrimental to losing weight. The body does not use up very many calories to digest and assimilate fat. It has been estimated that if a person eats 100 calories worth of protein or carbohydrates, the body will use up 25% of those calories to digest those nutrients. However, if a person eats 100 calories worth of fat, the body will only burn 3% in the digestion process.
Scientists have found that the more frequently we eat, the more energy we will expend in digesting the food. Thus, many dietitians and nutritionists recommend eating several - usually four to six - small meals a day. This is good advice; however, it comes attached with a warning. This strategy will only work if the composition of the food is low in calories and in appropriate quantities. This tactic does not work with snackers who get tempted into eating high calorie junk food. It would be better for them to stick to the traditional three square meals a day.
Adaptive thermogenesis (AT) represents the way the body responds to stress whether it is emotional or environmental (for example, changes in temperature). Typically, stressful situations result in an increase in calories burned.
Scientists are still not sure about how much it contributes to total daily caloric expenditure. Many of them think it may be an important factor in explaining why two people can be leading the same type of lifestyle in terms of exercise and diet and yet, have two completely different body types.
Adaptive thermogenesis may also include spontaneous and unconscious movements like fidgeting and not being able to keep still. Some people are just more "hyper" or nervous than other people who are more placid. The hyper-types may burn more calories.
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