I found this on pub med:

http://www.ncbi.nlm.nih.gov/entrez/q...&dopt=Citation

If the sciences makes your eyes glaze over, here is the conculsion:

In conclusion, these results reinforce the notion that for a given level of energy expenditure, vigorous exercise favors negative energy and lipid balance to a greater extent than exercise of low to moderate intensity. Moreover, the metabolic adaptations taking place in the skeletal muscle in response to the HIIT program appear to favor the process of lipid oxidation.

In other words, high intensity training is actually better for fat loss than endurance training. High intensity training spares the muscles - and muscles burn fat at a faster rate than fat. Endurance training tends to use muscle mass - not something you want if you're trying to lose weight.

Also, the notion that a calorie is a calorie is being disproved. Studies are showing and all things being equal (energy expenditure and calorie intake) women who eat a hgher protein diet lose more fat weight and retain more muscle than other types of diets.

Your husband will not build appreciable muscle on the bike. He needs to be in a gym lifting weights to build muscle.

I love my endurance training. I'd much rather ride 3 hours than do anything else. But, these days I keep it at a minimum, 1 - 2 times/week. I concentrate on hills, sprints and short rides at tempo for most of my riding. And I lift weights to retain/build muscle mass. I don't want to be one of those menopausal women who can barely carry groceries to the car.