Higher intensity exercise burns up more calories, promoting fat loss. Although lower intensity exercise (say about 50% maximum aerobic capacity or maximum heart rate) uses a higher percentage of fat for fuel, the total amount of fat used is less than for high intensity exercise.
It is often assumed that to burn fat, exercise intensity must be kept low. However, the bar graph shows that the amount of fat used is higher at 65% of maximal aerobic capacity (65% VO2max) than at 25%. At 25% VO2 max, fat accounts for almost all the energy used during exercise. However, the total number of calories expended over 30 minutes, is substantially lower (190 calories) than at 65% of VO2 max (420 calories). Although only 50% of the energy expended at 65% VO2 max is derived from fat, over the 30 minutes of exercise, this is a much greater amount of fat (210 calories of fat) than what is burnt at 25% VO2 max (150 calories of fat).
It is important to remember that aerobic training improves the body’s ability to burn fat, even when working at moderately high exercise intensities (around 60-70% VO2 max or maximal heart rate). To optimise fat loss, you need to work continuously for at least 30-60 minutes. As you get fitter you can exercise harder and still be in the ‘fat burning’ zone.
A comfortably challenging pace optimises both fat and calorie use, burning more fat in less time. Remember, untrained people need to start slowly. There is also benefit in accumulating three 10-minute periods of low intensity physical activity a day for those less interested in exercise.
Moving more by increasing incidental exercise (eg taking the stairs, walking to work) is a key weight control strategy.
Essential strategies for weight (fat) loss or making weight
• Choose a body fat/weight that keeps you healthy in the long term.
• Choose a balanced diet, emphasising a low-modest fat intake.
• Eat a little less energy (kilojoules/calories) than you burn in training or competition to achieve a slight calorie deficit, and therefore a healthy weight (or body fat) loss. Don’t crash diet.
• Learn how to handle eating out socially and include treats. You should not become obsessed about, or even frightened of, the occasional splurge.
• Have a training program that complements your weight (fat) loss strategies. If you need to make a specific competition weight, heavy weight training may need to be reduced or balanced with aerobic training.
• Be wary of times when weight (fat) levels may fluctuate more, for example ‘off season’ or injury. Monitor these changes and adjust your dietary intake and training to suit.
• Gradually reduce weight (not more than 0.5-1.0 kg per week) or 2-5 mm of fat each week if using skinfold (the pinch test) measurements.
• Train not more than 2.0 kg away from your optimal competition weight.
• Seek professional advice from a sports dietitian on dietary requirements for your sport, or whether a weight category or body fat level is realistic for your physique.
Low carbohydrate diets – just another low kilojoule diet
Just when most people appreciate that high carbohydrate foods like bread and potatoes are not fattening, a new era of carbohydrate controversy has emerged. A range of reduced or low carbohydrate diets has captured the imagination of athletes and fitness enthusiasts alike.
These diet plans commonly restrict the choice of foods you can eat and make meals more difficult to arrange because there are so many rules to follow.
The end result is that they all become a low calorie diet in disguise. At the start followers do not notice that they are eating much less, sometimes as low as 4000 kilojoules per day! This is less than half the calorie needs of a sedentary adult female.
It is no wonder short-term weight loss occurs. The claim made by low carbohydrate diet pushers that “fats are not fattening” is not supported by scientific research that provides a strong link between dietary fat intake and excess body fat. Following any low kilojoule and low carbohydrate diet, increases the risk of muscle loss and fatigue. See our Fact Sheet number 20 on Low Carb diets for weight loss in athletes.
