If you’re aiming to lose weight through exercise, spending hours at the gym may not only be unnecessary but could actually work against your goals, according to leading fitness experts.
Personal trainer Stephanie Mansour, a TODAY contributor and one of the trainers featured on the Start TODAY app, recommends keeping effective workouts in the 30 to 45-minute range. She describes this duration as the “sweet spot” for achieving meaningful fat loss, burning calories, building muscle, and maintaining long-term consistency without over-stressing the body.
Mansour explains that sessions shorter than 30 minutes often fail to provide enough stimulus for significant metabolic or fat-burning benefits, while workouts exceeding 45 minutes can lead to excessive fatigue, muscle soreness, increased injury risk, hormonal imbalances, poor sleep, and weakened immune function — all of which can stall weight loss or even contribute to weight gain.
The focus, she says, should be on quality, intensity, and consistency rather than marathon training sessions.
This guidance aligns with the Physical Activity Guidelines for Americans, which recommend at least 150–300 minutes of moderate-intensity aerobic activity or 75 minutes of vigorous activity per week.
For most people, this means five days of 30–45 minute moderate workouts or three days of higher-intensity sessions. Effective routines in this timeframe can include running, the popular 12-3-30 treadmill workout, kickboxing, Japanese interval walking, cycling HIIT, fundamental strength training moves, the classic 5×5 workout, or full-bodyweight circuits.
Experts emphasise that combining cardio and strength training within this optimal window, while prioritising proper form and progressive overload, delivers the best results for sustainable weight loss and overall health.