Dan, Denver is spot on here. Your max HR must be measured. Also, according to cycling coach and MD Arnie Baker, your HR max varies by activity, s a cycling max HR is different than a treadmill determined max. For example, my Max HR (cycling) is 193 and I am 50 and this is not unusual for the forum members. The old thing about the fat burning zone is based on studies that show at a lower HR you burn a higher percentage of fat, but it neglects that at higher HR you are burning so many more kcals that you are burning more calories. Since I have been spectacularly unsuccessful at losing weight through cycling I cannot comment on the best way, other than ride lots and eat less. The facts seem to be that you burn somewhere between 600 and 1000 calories per hour cycling, depending on your pace and your weight and condition (as you get into better condition you get more efficient with your calorie expenditure. And its really easy to eat more than enough food to offset the exercise burn-off. Even back in the day when I raced and trained 200-300 miles a week I never lost weight unless I made a real effort to cut my food intake. I really think the best advise is to ride to improve you fitness and most of all as an enjoyable pastime. The better you like cycling the more you will ride. The more you ride the better your chance at losing weight as long as you reduce your food intake to some reasonable level that still allows you to ride comfortably.