I hear some statements quite often. "You need to do aerobics for twenty minutes to start burning fat. Before that, you are only burning sugar." "Walking is better than running because walking burns fat, running does not."
There are many misconceptions about fitness, but none greater than the misunderstandings that abound about "fat burning". Why is this so? It is because fat burning is a complicated physiological issue that is not easily explained to or understood by the public. Somewhere along the way, the message that was passed on from the research scientist to the fitness professional and the media to the exercise participant was garbled. In trying to explain the mechanics of fat burning to the public, much has gotten lost in the translation.
It started about ten years ago when exercise scientists discovered that the higher the intensity of the exercise, the less fat you burned. This led to a slew of exercise videos touting "fat-burning" workouts at very low intensities. Aerobic instructors started to tell their clients that they weren't burning any fat during the first twenty minutes of aerobics. Super-fit individuals who, previously, were happy doing high intensity workouts were now doubtful about whether they were burning fat or not.
All exercise burns fat.
Our body needs energy to function. This energy is found in the food we eat. All foods are made up of fat, carbohydrates, and protein. For the sake of our discussion, we will leave out protein because it is not a primary source of energy except in times of starvation and prolonged illness. We will focus strictly on fat and carbohydrates, the two primary sources of energy under normal conditions. A calorie is a unit of measurement of energy. There are four calories per gram of carbohydrate and nine calories per gram of fat.
The body is constantly using a mixture of both carbohydrates (stored in the liver and muscles as glycogen) and fat (stored in the fat cells as fatty acids). There is no such thing as only fat burning or only carbohydrate burning during exercise or that there are two types of exercise - that which burns fat and that which does not.
Actually, all exercise burns fat. For every calorie your body uses at rest, approximately 50% comes from fat and 50% comes from carbohydrates. Some studies have found that if you are a fit individual, 70% of that calorie can come from fat.
Therefore, technically speaking, resting in bed could be considered a "fat-burning" exercise! Of course, resting is not a very good way to burn a significant amount of fat because very few calories are used up lounging around in bed. Don't get me wrong, I am not, repeat, not advocating being sedentary as a way to lose fat!
How exercise intensity affects burning fat calories.
Having established that the body burns a mixture of carbohydrate and fat, let us now proceed to see how increasing exercise intensity affects this mixture. As you increase your exercise intensity, going from rest to, let's say, walking briskly, you will (don't faint!) burn less fat per each single calorie. As you increase the intensity even more by going from walking to running, you burn even less fat and more carbohydrate per each calorie your body uses. So it is true that the higher the intensity of the exercise, the less percentage of fat you burn. But that "truth" can be misleading because less percentage of fat does not automatically mean less total volume of fat burned! Read on.
A big pie versus a small pie.
When you run (exercise harder), you breathe in more oxygen than when you just walk. For every liter of oxygen that you consume, you burn approximately five calories. Therefore, at the end of a 30-minute run, you will have consumed a larger volume of oxygen (more calories burned) than if you had walked for the same length of time. High intensity exercise uses a smaller percentage of fat but a larger total number of calories burned.
An exercise physiologist named Owen Anderson, put it this way: a small part (smaller percentage of fat per calorie at a higher intensity) of a big pie (more total calories burned) can be just as big or bigger than a larger piece (bigger percentage of fat per calorie at a lower intensity) of a smaller pie (less total calories burned).
I don't like math much either but get out your calculator and let's look at a hypothetical case.
- Lower intensity exercise for 30 minutes.
- Total number of calories burned = 240
- Percentage from fat = 41% = 98 fat calories
- Higher intensity exercise for 30 minutes.
- Total number of calories burned = 450
- Percentage from fat = 24% = 108 fat calories
In case you were wondering, a machine called a metabolic gas analyzer that calculates how much oxygen a person consumes while exercising measured the percentages of fat. Don't expect to see this gadget any time soon on your favorite home shopping network. It's only available at exercise laboratories in large universities or research facilities.
Determining exercise intensity.
How exactly does one determine the intensity of an exercise? I won't get into the technical definition (40 - 50 % of your maximum heart rate etc.) but would like to give you a practical way to determine whether an exercise is low, moderate or high intensity. This method is called the "ratings of perceived exertion" or RPE. You rate the intensity of the exercise according to how it feels or how you perceive it to be.
Low intensity exercise feels very comfortable. You are breathing easily, you can carry on a conversation, and you feel like you could go on for hours. Walking at a leisurely pace would be a good example.
Moderate intensity would feel like you are breathing a little faster, you can still carry on a conversation but you are huffing and puffing a bit. An example would be brisk walking.
During high intensity exercise, you can feel your heart thumping, you are breathing hard and you can talk but only in very short sentences. Running, an advanced aerobics class, or a singles tennis match would be a good example.
Super-high intensity would be hardly being able to talk and gasping for air. The 100-meter dash would be an example. At this level, the body is burning almost all it's calories from carbohydrates.
Another important fact to remember about exercise intensity is that it depends on the fitness level of the individual. A very unfit individual may perceive brisk walking to be a high intensity exercise while an extremely fit individual may find the same activity to be very low in intensity.
Each intensity level has its advantages and disadvantages. Low intensity exercise is perfect for unfit people and obese individuals. The advantage is that low intensity exercise is something they can do without injuring themselves and putting too much of a strain on their cardiovascular system.
Also, it has been found that low intensity exercise is beneficial for those with Syndrome X, a cluster of risk factors that include insulin resistance, low HDL cholesterol (the "good" cholesterol), mild hypertension and elevated triglycerides (a type of fat found in the blood).
The disadvantage is that to burn a significant amount of calories, you have to do it for a much longer period than moderate or high intensity exercise.
If you are a fit individual, you have the advantage of choosing time-efficient moderate or high intensity exercises. You can challenge yourself to work out as long as possible at as high an intensity as possible to maximize calorie burning. This is assuming, of course, that you enjoy high intensity workouts (some people don't, no matter how fit they are) and that by doing so you will not ruin your knee, shoulders, and back joints! Your heart and lungs may be fit enough to run kilometers everyday but your knees may not. Compromise and choose exercises that challenge your fitness level but are still safe for the rest of your body.
Super-high intensity training is usually only done by elite athletes training for specific sports.
Are fat cells really with you forever? Is there any way to get rid of them permanently?
Yes, fat cells are with you forever. They don't disappear when you lose weight, they only shrink. When you gain weight, they enlarge. They can only be removed permanently through surgical procedures like liposuction.
If I have liposuction, does this mean I'll never get fat again?
The fat cells removed by liposuction will never come back again, however if you continue to overeat and remain sedentary, the other fat cells in other parts of your body (or even the same part that got "vacuumed") will gladly enlarge with excess fat. You cannot fool the body; it has to store the additional calories somewhere!
Will my muscles turn to fat if I stop exercising?
No, no, no. This must be one of the oldest myths that exist about fat burning. Fat cells cannot turn into muscle cells or vise-versa in the same way that your bone cells cannot turn into your blood cells. Muscle cells can enlarge or shrink the way fat cells can. Muscles become heavier and denser with exercise while fat cells shrink if you burn enough calories. When you stop exercising for a long time, the process will revert itself - muscles atrophy and fat cells enlarge if you overeat. To the naked eye, it might seem as if the muscle has turned to fat.
Will lifting weights make my fat hard?
Some overweight people believe that they need to lose weight first before they can do a gym workout otherwise their "fat will get hard". This is not true because fat cells do not "harden" in response to weight lifting. Muscle fibers, on the other hand, get slightly larger thus feeling "harder". If an individual lifts weights and consumes an excess of calories, they may observe that their "fat is getting harder" because the muscles are enlarging and pushing against a fat layer that has not gotten any smaller.
Lifting weights or resistance training aids fat loss by increasing your lean body mass (how much of your total weight is not fat) so you can burn anywhere from 50 to 100 calories more per day even at rest. The more muscle mass you have, the more calories you burn. You can lift weight to lose weight!
Is there any truth to the claim that cellulite is not a fat problem but rather a skin problem?
Biopsies reveal that there are no differences between fat cells taken from a person with cellulite and a person without it. Thin women, even athletes, can have cellulite while there are obese women who do not. So it does seem that there is truth to the claims of cosmetic companies like Estee Lauder (ThighZone) and, recently, Clinique (Firm Believer) that cellulite is ordinary fat under a special kind of skin. Now, as to whether their gels and creams can actually strengthen the structure of cellulite prone skin and not just temporarily improve its appearance remains to be proven conclusively.
Is it true that the fitter I am, the more I can burn fat?
Yes, your body adapts to aerobic training by increasing your stamina, the capacity of your lungs to take in more oxygen and the efficiency of your muscles to use that oxygen to burn more fat. Fitter individuals will also challenge themselves by exercising harder, thus taking in more oxygen, and burning more calories. Some studies show that a fit individual will burn more calories from fat at rest than a sedentary individual.
Can I burn fat from specific areas of my body by doing "spot exercises"?
Current research indicates that you cannot "spot-reduce" fat from specific areas of the body. Tests done on tennis players show that their dominant arm (the arm they use to swing the racket) is bigger, has more muscle mass but has the same fat percentage as their inactive arm. Exercise stimulates fat reduction throughout the entire body, not in localized areas. If you could choose the exact areas where you wanted to burn fat from by doing specific exercises, then obese people who chew gum the whole day would have slim cheeks! "Spot exercises" are good for making specific muscles firmer and tighter.
Why do I always put on fat in my thighs while my friend puts on fat in her abdomen?
There are genetic and hormonal reasons why fat is not evenly distributed throughout the body. Women tend to get fat around their thighs, hips, and buttocks while men usually put on fat around their waist and abdominal area. This is the classic pear versus apple shape. If you are pear shaped, your hips and thighs are the first area that will get fat if you gain weight while your friend may be an apple and her abdomen will the area that will get bigger first when she becomes overweight.
Is it easier to lose fat from the abdomen than from the hips and thighs?
Research does tend to show that it is easier to lose fat from the abdomen than from the hips, thighs, and buttocks area. Scientists think that this may be because the reproductive hormones in a woman's body somehow regulate the fat that is stored in the hip and thighs area. While pear-shaped individuals may be very frustrated with their "saddlebags", at least this type of fat distribution pattern is not related to health problems. Apple-shaped people, meanwhile, have an easier time losing their abdominal fat but are at risk for high blood pressure, diabetes, and hyperlipidemia (elevated levels of fat in the blood).
Is it true that the more I sweat, the more fat I lose?
Not necessarily. If you sweat because you are exercising in extreme heat or humidity or because you are wearing "rubberized" clothing, the weight lost is only water and not fat. When you eat and drink, those lost pounds return almost as fast as they left. Since you have to burn 3,500 calories to lose one pound of fat, do not be fooled into thinking that the three pounds you have lost by staying twenty minutes in a steam room is composed of fat.
Don't be fooled either into thinking that if you are not actively sweating while you are exercising, very few calories are being burned. Running on a treadmill in an air-conditioned gym will probably produce less visible sweat than taking a five minute leisurely walk outside in the heat of the noonday sun and yet, will burn many more calories.
What is the best way to measure fat loss?
The best way to measure fat loss is through body composition testing. The weighing scale alone is not accurate because it only gives you your total weight. It does not tell you how much of your body is lean and how much is fat. The scale might tell you that you are five pounds lighter after a severe bout of intestinal flu but the weight lost is probably due to dehydration more than any significant amount of fat being burned.
There are many body composition testing techniques available, some more accurate than others but all techniques will only give you an approximate measurement of your body fat. These techniques include hydrostatic or underwater weighing, skin fold measurements done with a special caliper, and bioelectrical impedance measured with an electrical impedance machine. The most accurate, no fail technique? Have your fat weighed after you die! Unless you have access to a research laboratory or an up-to-date fitness center, the most practical method to use is the way you fit into your clothes.
Is it true that if you were fat as a child you will be fat as an adult?
Having been fat as a child does not doom you into being a fat adult but it definitely increases your chances. Studies indicate that if one parent is overweight, a child has a 40 % chance of becoming overweight too. If both parents are overweight, then those percentages rise to 70%. In comparison, the child with normal weight parents only has a 7 % chance of becoming obese. Researchers still don't know whether this is due to heredity or bad eating and exercise habits passed on down by example or a combination of both.
Is it true that I can eat as much as I want and not gain weight as long as the food is low in fat or as long as I am exercising?
All excess calories, whether they come from fat, carbohydrates or protein, will be converted to fat. Non fat or low fat food does not mean zero calories! Long and intense workouts do not guarantee that you can eat whatever you want and not gain weight. If the amount of calories you eat is greater than the amount of calories you burn, chances are extremely high that you can still gain weight.
My aerobics instructor told me that I only start to burn fat after 20 minutes. Is this true?
As we mentioned last week, the body is constantly burning a combination of fat and carbohydrates. For every calorie you burn at rest, approximately 50 % of that calorie comes from fat and the other 50 % from carbohydrates. We are continually burning both nutrients throughout the day but at different percentages depending on the intensity of our activity.
Total calories more important than fat calories.
Most experts feel that it is not important what percentage of the calories burned come from fat or from carbohydrates. What is important is how many calories are burned for any given activity and whether you enjoy that activity or not. Don't get obsessed about how much fat you are burning. Just pick the exercises you enjoy at the intensity you are comfortable with and "just do it".