The simplest way to understand how your metabolism works is to think of it as the energy your body needs just to be alive. Basically, you can think of your body like an engine that needs fuel to power it just to stay on. However, unlike a car engine, which can be shut off, your body’s engine never shuts off until you die. Even when you are asleep, you are still burning fuel to power the ongoing systems of your body, which includes your respiratory and cardiovascular system, digestion, body temperature, and cellular functions and rebuilding. One thing to remember is that your body rebuilds itself constantly from the inside. Even after we become adults and stop growing, our body still replaces worn out cells with brand new ones. Physiologists call the caloric (fuel) needs of a body at rest the “basal metabolic rate” or BMR. Common sense tells you that the bigger a body you have, the more calories it will burn at rest to keep it functioning. But, your metabolism is also related to how much muscle you have as opposed to fat, since a muscle cell is used more for everyday functions, it will also use more calories at rest. So body composition (body fat vs lean body mass) is also a determinant of what your BMR is.
Exercise physiologists William McCardle and Frank Katch came up with a simple formula that you can use to estimate your BMR once you have your Body Fat % measured. It is:
BMR (men and women) = 370 + (21.6 X lean mass in kg)
You are female
You weigh 120 lbs. (54.5 kilos)
Your body fat percentage is 20% (24 lbs. fat, 96 lbs. lean)
Your lean mass is 96 lbs. (43.6 kilos)
Your BMR = 370 + (21.6 X 43.6) = 1312 calories
REMEMBER, that is the calories needed just to maintain yourself if you were lying in a bed ALL day. This is not your maintenance amount of calories if you do any activity at all, including just sitting at a desk. To find out what your maintenance level of calories would be, you have to factor in your activity level. Below is a chart to help gauge this number which is your Total Daily Energy Expenditure needs (TDEE):
Sedentary = BMR X 1.2 (little or no exercise, desk job)
Lightly active = BMR X 1.375 (light exercise/sports 1-3 days/wk)
Mod. active = BMR X 1.55 (moderate exercise/sports 3-5 days/wk)
Very active = BMR X 1.725 (hard exercise/sports 6-7 days/wk)
Extr. Active = BMR X 1.9 (hard daily exercise/sports & physical job or 2X day training, i.e marathon, contest etc.)
Your BMR is 1312,
Your activity level is moderately active (work out 3-4 times per week)
Your activity factor is 1.55. Your TDEE = 1.55 X 1312 = 2033 calories
According to exercise physiologists McArdle and Katch, the average maintenance level for women in the United States is 2000-2100 calories per day and the average for men is 2700-2900 per day. These are only averages; caloric expenditure can vary widely and is much higher for athletes or extremely active individuals. Some triathletes and ultra-endurance athletes may require as many as 6000 calories per day or more just to maintain their weight! Calorie requirements may also vary among otherwise identical individuals due to differences in inherited metabolic rates.
Calculating your TDEE is very useful for planning any weight loss program. Basically, you would want to create a slight caloric deficit (15-20% of TDEE) in order to lose body weight, but you have to be careful that you also maintain a lifestyle that helps you lose fat and not muscle, or you could wind up with deceptive results (more about this later).
Most of us don’t know our exact body fat % or our TDEE. However, if your weight hasn’t changed in several years, you can still figure out some important information that you can use to reduce your body fat. If your weight has been consistent, than you are in a homeostasis (metabolic balance) in that your body is maintaining a fairly steady weight. Most of us will over eat some days and under eat on others. Even with these variations in our caloric intake, our bodies will adjust metabolically to settle back to what it feels is our regular weight. The formulas above make it look like all you have to do is establish a negative caloric balance from your usual TDEE and voilà, the fat will burn off. The truth is that is a little more complicated than that, especially at first. This is one reason it is so hard to lose weight just through exercise. In terms of establishing a negative caloric balance, you can burn 250Kal on the elliptical (around 30 minutes) and cut out 250Kal from your diet daily and you still might not lose a whole pound each week, even though formula wise, 7 x 500 = 3,500K which equals one pound of fat. The reason is your body is going to fight going down to a weight it is not used to. I have found that you actually have to hit specific targets in terms of exercise and diet and maintain them for several weeks, before the body accepts the change permanently and resets itself with a new metabolism matched to your new weight.
One of the exercise targets that absolutely must be met is to increase your cardiovascular endurance to where you can do 45 minutes to an hour of steady aerobic exercise. Studies have shown that for the first 45 minutes of aerobic activity, your body will derive most of it’s energy from the carbohydrates floating in your bloodstream and in your muscle cells. Only a small percentage of your energy needs come from fat during this time since fat is harder to break down and it doesn’t have the need for using it as fuel yet. After you go past 45 minutes however, the metabolism will kick into burning fat mode, using it as its primary source of energy to support your aerobic exercise. So, someone who does 30 minutes of cardio every day may still be frustrated from not seeing fat loss results because they never reach the 45-minute threshold. I actually don’t recommend anyone to do 7 days a week of cardio, nor do I think you have to. Five days a week of exercise is plenty to reach the 3,500K goal, especially if you add some weight training into your fitness program. Which is exactly what you want to do if you want to lose body fat, because increasing muscle tissue has been proven to increase the metabolism. Twice a week should be enough for the strength training to have a noticeable effect. However, there is an interesting phenomenon with the two different forms of exercise; strength training has been associated with an increase in appetite, while moderate aerobic training hasn’t. So, you should do both kinds for best results. For most people, they should build up to doing 4 – 5 days of cardio training, with 2 workouts lasting over 45 minutes long. On the other 2 days of cardio, you could try doing shorter “interval training” workouts, which have been shown to help people lose weight faster than plain steady pace aerobics [please see following article on Interval Training Plan].
In terms of diet, of course you have to cut some calories if you want to lose weight, but again, you need to be really careful how much and when you do this or you can really sabotage your system. A lot of people find breakfast the easiest meal to skip. This is a big mistake. You don’t have to eat breakfast right away in the morning, but you should try to eat within 2 hours of getting up. That means you could even go for a 45 minute run after you wake up (drink at least 8oz water before), and then come home, shower, and then eat and you would still be within the guidelines. What is not good, is skipping breakfast and not eating anything until 4 hours later. By that time your metabolism will have reset itself into starvation mode, which is a low calorie BMR, and even small amounts of calories will be more than your body will be ready to burn so it will be more likely to be stored as fat. It really isn’t the calories that will hurt your goal, it is the lowering of your metabolism over time that is the sabotage that skipping breakfast will cause. Skipping any meal will hurt your metabolism because it get’s partially turned on by regular timing of your meals. Now, if one day you are really sedentary, you might be able to eat breakfast, and lie down and just read for hours on just a cup of tea. So, activity does play a key part in the timing and quantity of food you would want to consume. If you are having a normal active day, the four-hour rule is a pretty good one to be conscious of, meaning you should eat something every four hours, even if it is just a snack, in order to keep the metabolism charged.
The quality of the foods you eat is also vitally important to your health and to maintaining a healthy weight. The worst in terms of foods that hurt your metabolism are sugary ones, also known as simple carbohydrates. Breakfast again is the meal where people are the most neglectful of this. It never fails that most of the people who buy the glazed donut or super sized caramel mocha latte are overweight. Eating sugary foods for breakfast are the worst thing you can do to your energy system. They take the metabolism, by way of your glucose levels, on a roller coaster ride. Riding up for a few short minutes, then crashing down for hours afterwards. The best thing to have in the morning is protein, a little fat, and some complex carbohydrates. In terms of actual food, that could be 3- 4 egg whites and some whole-wheat toast with Smart Balance spread. You could eat an orange as well, or later as a snack before lunch. There is enough fiber in the orange pulp to help offset the sugar in the juice. But, just a glass of juice or a fruit based smoothie in the morning is not the best idea for a fat-loss lifestyle.
The end of the day is also a time to be mindful of eating. Generally, your metabolism slows down the later in the day it gets. Therefore, eating big meals really late at night is a lifestyle habit you should try to break. If you work at night, plan on eating an early dinner right before work, and then eating only lightly afterwards, like vegetables or salad. When we are tired at the end of a long day, our willpower is also tired. That means that fattening comfort foods and desserts start looking better the later the hour gets. Be conscious of this and just avoid the temptation by not having them around you and hitting the hay sooner rather than later.
Lack of sleep is a stressor, and like stress in general, it has a negative effect on the metabolism. Studies have shown that living under stress causes the body to release extra amounts of cortisol, which is a hormone that causes the body hold onto fat. More than that, studies on sleep deprivation show that being tired causes your body to lose its sense of “satiation”. Normally, after you’ve eaten, the body releases a chemical that tells the brain it is full, and this makes you no longer crave food. If you are sleep deprived, this chemical isn’t released so you never feel satiated. This explains why late night binging is so common in people with eating disorders.
So, in conclusion, to lose fat properly means to look at where you are in terms of current weight, activity level, diet, and lifestyle and making sure you pay attention to each aspect. Everyone is different in terms of what is best for his or her individual situation. However, there are common rules about the body that anyone can use to help lose fat and look leaner. To summarize, here are the steps you can take to get better control over your metabolism and body fat:
A. If possible, find out what your body fat % is right now. Many health clubs offer this free as a part of your membership, or you can ask a trainer to measure it for you. I personally prefer the Lange Skinfold Caliper measure. After that, use the formulas provided above to figure your Lean Body Mass(LBM) and then calculate your BMR = 370 +(21.6 X LBMkg)
Then you multiply your BMR times your activity factor (see above) to find your TDEE, which is the number of calories you need to consume to stay the weight you are now. This is a good number to know just for your own information, and can help guide you if you start to measure your caloric intake for a weight loss program.
B. If you don’t know your BF%, you can still begin a sensible program to reduce your body fat percentage by following the specific exercise, diet, and lifestyle rules summarized here:
1. Do aerobic exercise 4 – 5 days a week, start with one of those days being a longer workout of at least 45 minutes within your training heart rate, and then try to increase to two long cardio days each week. The other two days of cardio should be shorter in length (25-30min) with one being an interval speed workout if running, or interval incline workout if walking.
2. Do resistance training (strength) at least twice a week. The easiest plan would be to do a full-body routine each day, starting with large muscle groups (legs, back, chest) and then smaller muscle groups (shoulder, biceps, triceps). Hit your large muscle groups with two exercises each, doing one warm-up set and two progressive sets, meaning a little heavier each time. Hit your smaller muscles with at least one exercise each, two sets each. You also want to do abdominal exercises and stretching, which you can accomplish in a Pilates class!
1. Creating a negative caloric balance between what you consume and what you expend is of course essential to losing weight. However, if you weren’t exercising at all before, you will be creating a negative caloric balance just from that. Try just reducing your portions slightly (200K a day) and keeping healthy snacks like fruit, nuts, and non-fat yogurt around if you need an energy boost.
2. Make breakfast a conscious choice each day. Remember, you can exercise before breakfast as long as you can do that and still get to eating within two hours of when you wake up. Also, you will support your metabolism better if you choose lean protein as the main ingredient in your breakfast choice.
3. Stay away from sugary foods; this includes many boxed cereals (check the labels), candy, desserts, pastries, and sugary beverages such as soda or canned or bottles ice teas. Even those with artificial sweeteners still affect the metabolism negatively.
4. Don’t skip meals entirely. If you have a sedentary day of rest, you could eat lightly(small portions), but don’t let too much time(over 4 hours) go by with an empty stomach.
1. Try to eat dinner earlier rather than later. The later it gets, the slower your metabolism is.
2. Learn how to cope with stress so you minimize its effect on your metabolism. Luckily, exercise is one way to combat stress, both physical and mental. Nevertheless, you may want to investigate meditation and lifestyle coaching to help you deal with persistent stress and its negative health effects.
3. Be patient. Remember that body fat is pretty stubborn stuff. You will probably start to lose it where you have it least (face, neck, back) and from your main problem areas last. There is no such thing as spot reduction, meaning you can do exercises for the back of your arms all you want, but that only works the muscles, possibly building them bigger if you do too much, and won’t touch the fat that covers them. Body fat, no matter where it is stored, is used for energy; it can’t be changed from fat to muscle. So, the best way to burn it is to up your metabolism, as described above.
4. Be consistent and enjoy yourself. Find friends to work out with, or go waking with your dog. You can use music to motivate yourself as well. Keep the faith, you will succeed if you just stick to it.