My resting hr is 58, when i was very fit it was around 50 (age 20). Now, making allowance for weight (190) at age 64 i try not to exceed 130 bpm. Today i lost 3.5 pounds on my ride. I weigh myself before i ride and try to get enough water and food to come close to my starting weight. I usually stay between 110 to 120 bpm for max weight loss. I weighed 155 at age 20. My goal is 165 pounds, should take about a year to year and a half. I will do it by increasing my distance keeping the same rate. I am sure i could get up to 150 to 160 bpm with no harm but will take the less stressful route.