First, and most obvious, is the energy required to move you and your bike against the resistance of air and gravity. A second, more indirect effect is through subtle changes in your daily routine to include more physical activity (such as walking up a flight of stairs instead of taking the elevator) because of an increased sense of vigour and well being.
Many dieters worry that increased physical activity will increase their appetite. However a recent, carefully controlled, study of overweight individuals did not reveal a proportionate increase in appetite with exercise, lending support to the positive role of physical activity in reaching the goal of a negative Caloric balance and resulting weight loss. In fact, vigorous exercise actually suppressed appetite for several hours, suggesting that this short term effect can be used as an effective appetite control strategy by planning your exercise immediately prior to your major meal of the day.
Regular exercise also increases your basal metabolism rate or BMR (the number of Calories utilized by the body at rest to maintain basic life processes). An increased BMR is associated with all aerobic conditioning activity and is maintained with as little as 30 to 40 minutes of exercise 3 to 4 times a week. One study indicated that the increase in BMR with regular exercise might be even more pronounced in the older athlete.
Not only is there an increase in your overall BMR with regular exercise, there is an additional 12-hour post-exercise boost in the BMR. As a rule of thumb, this adds 15 bonus Calories for every 100 Calories burned during your aerobic activity. To capitalise on this post exercise bonus, consider two (or more) rides per day - perhaps in the morning and after work - rather than a single ride.
Finally, regular physical exercise will protect muscle mass (at the expense of fat) during periods of weight loss. In two groups (one active and one more sedentary) with an equally negative Caloric balance and an equal weight loss, the exercise group will lose less muscle mass than the diet only group.
A common question is whether exercise can facilitate selective fat loss from the limb(s) exercised i.e. can fat be taken off the thighs by bicycling. Unfortunately this doesn't happen. Take the extreme example of a regular or professional tennis player who uses one arm almost exclusively. Comparison of fat fold thickness in both arms will NOT demonstrate a difference, or asymmetry between them. Thus any exercise will promote fat loss from the body as a whole but cannot be targeted to any specific body area. However, there is still the benefit of improving the tone of the muscle, or muscle groups exercised which has the same apparent affect to "slim" the area.
Some have suggested that riding at slow speeds (<50% VO2 max) is preferred for a weight loss program as more of the Calories expended will be supplied from fat tissue storage at lower levels of exercise.
If you ride at 65% VO2max, your body's fat stores will provide about half of your Caloric needs and the other half will come from glycogen reserves.
At 85% VO2max, the relative number of Calories supplied from fat fall to about one third of the total number expended with the balance again coming from glycogen reserves.
However, if one looks at the absolute numbers, a fit cyclist riding 30 min at 65% VO2max will burn about 220 Calories (110 fat Calories, 110 Calories from carbohydrate or glycogen stores). The same cyclist, riding at 85% VO2max will burn an additional 100 Calories (total of 320 Calories over the 30 minutes), with 110 Calories still coming from fat and the balance of 220 coming from carbohydrates. So even though fat provides a smaller percentage of the total energy needs, the actual number of fat Calories burned during the 30 minutes of exercise remains unchanged.
Even if the duration of the faster ride were shortened so that total Calories expended were equal (but proportionally more fat Calories with the slower pace) during both rides, a recent study demonstrated an equivalent weight change i.e. there was no support for the idea that metabolising fat for energy resulted in a greater weight loss.
Another study assigned 15 women to a low intensity (132 beats per minute), or high intensity (163 bpm) exercise group, both exercising for 45 minutes, 4 times a week. There was a decrease in overall body fat in the high intensity group, but not the low intensity one, further evidence that it is total Calories expended, not the source of those Calories (CHO vs. fat) that makes the difference in an exercise supported weight loss program.
It is the final balance between total Calories burned (from ANY source - carbohydrates, fats, or protein) and those eaten (i.e. the NET NEGATIVE CALORIC BALANCE) that determines whether weight is gained or lost. The advantage of riding more slowly is that it may make the ride a more enjoyable experience for the novice rider, and the pace can be maintained for hours. If you have only a limited amount of time to ride, the faster your average speed, the more Calories you will burn and the more weight you will shed.
In fact there has been speculation that when you exercise at a slow pace, and preferentially burn fat Calories while maintaining muscle glycogen stores, any post ride carbohydrate loading may find the "tank full" (i.e. muscle glycogen stores) so to speak, and any additional carbohydrate Calories will be converted into fat instead. The bottom line is to ride at a pace that is comfortable for you, push yourself occasionally for the cardiovascular benefits, and avoid eating more Calories than you expend if your goal is to lose weight.
Another suggestion has been that caffeine (3 to 4 cups of coffee) per day, because of its enhancement of fatty acid metabolism, would facilitate weight loss. There is no evidence to support this approach, perhaps related to the fact that the regular use of caffeine eliminates this particular physiologic effect.
FOUR PRACTICAL TIPS
- Dieting alone doesn't help You will lose weight, but it will be more than fat. Some is muscle (which actually burns Calories for you!!) and can leave you thinner, but also slower and weaker. And with less total muscle mass, a return to pre diet eating patterns can actually lead to more rapid weight gain and stabilization at a higher level than where you started.
- Ride This will help to maintain your muscle mass while you are shedding fat. And even at a recreational pace of 15 MPH, 1 hour a day of riding will burn almost 4000 Calories per week (the equivalent of a pound of fat) in addition to your normal activities.
- Eat a high carbohydrate diet The diet that is best for endurance performance (60 to 70% carbohydrate, low in fat) is also the best for weight loss. And small changes will add up - cut that portion of meat or chili in half, and add potatoes, rice, or pasta to make up the difference; eat bagels instead of muffins (which usually contain oil); substitute yogurt for sour cream or fruit for desert.
Do some weight training This will help to maintain muscle mass, and as riding uses mainly the lower body muscles, it will help to protect the upper body during this time of negative Caloric balance. A program of 20 to 30 minutes three times a week will maintain what you have already. And the increased muscle tone and positive feeling that go with it are a big plus to keep you on track.