What is the best exercise for a woman over 40 to lose weight?

Maggie Topham puts it simply: cardio burns calories only while you're doing it, and muscle burns them 24 hours a day, even while you sleep. After 40, women lose 3 to 8% of their muscle per decade without resistance training. Nikkiey explains that this muscle is your metabolism, so losing it year over year lowers what your body burns at rest. She adds that cardio may burn slightly more per session, but a woman who builds five pounds of muscle over a year burns meaningfully more every single day.

The show also argues that heavy cardio can work against you. One WarriorBabe coach describes constrained energy expenditure: your body adapts to lots of cardio by cutting energy use elsewhere, so the treadmill's calorie count overstates what you burn. Another coach says this adaptation often leads to a plateau within six to eight months. The coaches also say long, moderate sessions raise cortisol, which in their view encourages belly fat and muscle loss after 40. If you're piling on classes and still getting more tired and puffy, the show's message is that nothing is wrong with you. The plan is the problem.

There's nuance. One coach stresses that cardio isn't bad, just that you don't need a ton of it. Runners can keep running if they eat enough to fuel it. And age isn't a barrier: Nikkiey says her oldest client deadlifted for the first time in her late 70s. If you have a medical condition, check with your doctor before starting a new program.