Exercise - Free Fitness Library
Does Aerobics Make You Fat?
By Jon Cossins
There are many media pundits and fitness instructors who believe that in order to lose weight (i.e. burn fat) you have to perform cardiovascular (aerobic) activity. After all it uses large muscles, makes you sweat and uses large amounts of energy.
What they fail to tell you is that 70% of the energy you use is in the form of carbohydrates, only 30% is fat and that fat is readily available for energy respiration in the blood stream in the form of cholesterol not the lumpy stuff around the thighs and buttocks.
Actually, the sums are quite simple. In an aerobic class of say 40 minutes or using one of the many cardiovascular machines in the gymnasium you will use about 300Kcals by working at high levels of intensity. In fat terms that 30% is worth about 6.66 grams of fat. There are 289 grams of fat in 1lb of fat mass:
289 ÷ 6.66 = 43.30 mins aerobic workout to lose 1lb fat
After each workout your metabolism will be elevated for some time but not enough to make a significant impact on that stored fat. That is not all the bad news however. Research by Westcott 1995, 1996, when evaluating the effects on Aerobics Only vs. Strength Plus Aerobics found that those performing Aerobic Only lost one half pound of lean tissue (muscles) during a 10 week study.
The significance is that by losing muscle your metabolism will be lowered. Muscle tissue is very energy demanding. One pound of muscle requires as much as 35-50Kcals of energy per day. The research featured here shows that 72 overweight men and women took part in a research study. They followed the same dietary guidelines and exercised 30 minutes a day, three days a week for 8 weeks. 22 Performed aerobic exercise only and 50 performed a combination of aerobic and strength exercise.
Subjects who performed strength and aerobic exercise lost more weight than those who performed only aerobic exercise. More importantly, the subjects who performed both strength and aerobic exercise lost an average of 10lbs of body fat and gained 2lb of muscle - a 12lb improvement in their body composition.
The key to fat weight loss is not aerobic activity, cardiovascular exercise is significant for doing what it say - improving the vascular system and the heart. If you want to lose fat weight try strength training and with 3 sessions per week measure the changes.
Dear Jon…
Jon, I love exercising and being in the gym, I go every day and have
now progressed onto a split system which my instructor says should work
for me. The problem is I'm not making any significant gains and I'm
always tired.
Firstly, well done on your commitment to your exercise programme. The probable reason for you not making the muscular gains that you are looking for is that you are overtraining. Simply, overtraining occurs when the stimulus of training exceeds the body's ability to recover and adapt. It has been defined as decreased performance despite increased or maintained training load.
THE MAJOR SYMPTOMS OF OVERTRAINING
PERFORMANCE
Inability to meet previous performance standards
Prolonged recovery
Decreased muscular strength
Increase perceived exertion during submaximal exercise
PHYSICAL
Chronic fatigue
Increased heart rate at rest and exercise
Weight loss
Loss of appetite
Increased flu-like symptoms
PSYCHOLOGICAL
Feelings of depression
General apathy
Anxiety or fear of competition
Almost giving up when the going gets tough
BIOCHEMICAL
Decreased red blood cells
Decreased serum irons
Decreased haemoglobin
Decreased muscle glycogen
Increased lactic acid
Source: Kyle J McInnes Sc.D, University of Mass. Boston
If you are showing any of the symptoms above try cutting your workout
time by half. Check the intensity levels that you are working at and
try a pre-exhaust strength training programme, with two exercises per
muscle group and one set per exercise. Work hard and smart.
As you enjoy going to the gymnasium so much keep that up but while you
are there on your non workout days Relax, chill out, take a swim, sauna
or steam and enjoy yourself. Good luck!!