...My friend cycled daily around the area where she lived but did not seem to notice the weight loss
This is a touchy subject but here goes my $.02 cents and no need to bash me. Women are different than men as far as weight reduction. "Typically", it's more "challenging" for women to lose weight doing the same exercise as men for the same period of time at the same effort. If you ride 50 miles a week and lose 10 lbs after one month of riding, your friend may only lose 5 lbs. or less. It's just a physiological thing.
Most humans only lose weight when the calories being used are more than the calories eaten. Each person's metabolism is different. Me? I lose weight at the drop of the hat even at 63. I'm down 25 lbs from the beginning of the year after I ended my "Covid fortification eating regimen".
Long ago I stopped telling my lovely wife of 28 years how much weight I lost riding. She's just, "not interested". She did say the other day though that, "Those shorts look big on you". Progress!!