ride stationary bike six days per week for 20 minutes each, going ca4.2 to 4.4 miles each time then do 10 weight machines. Am 65 years old, weigh ca 221lbs. Is this enough exercise? Have tried to cut out carbs, don t drink alcohol, smoke, very seldom have sugar. What must I change to loose more weight? Most frustrating is not tightening muscles below my navel. Please advise.