You Might Be Undoing Your Own Progress (Let’s Fix That Right Now!)

YES, dude!

I love it when research backs what I’ve been saying for years.

If you know me, you know I’m a huge fan of HIIT (high-intensity interval training). Not just because it gets the endorphins flowing like crazy, but because of the seemingly endless benefits it has on the body.

A Feb 2026 study in the Journal of Functional Morphology and Kinesiology compared HIIT to LISS (low-intensity steady-state cardio like jogging or slow Stairmaster) in 24 adults over 12 weeks.

Both groups trained the same amount of time, 3 days per week. Both groups lost a similar amount of fat and had similar reductions in waist and hip measurements (awesome!).

But here’s the cool part:

The HIIT group had a slight increase in muscle mass (+0.47kg) whereas the LISS group had a slight decrease (-0.16kg).

This is so important to understand. It always comes back to muscle.

Losing fat is great! But if we're losing muscle along with it, it’s not a win.

If you care about your metabolic health, your physique, your long-term health… Muscle is your best friend. You want as much of it as possible, and you definitely don't want to be doing things that actively cause muscle loss – like lots of steady state cardio.

Muscle helps you by:

• improving insulin sensitivity
• increasing the amount of calories you burn at rest
• improving metabolic flexibility (your ability to switch between fuel sources)
• giving your body shape
• protecting against age-related decline in strength and function
• contributing to long-term healthspan and independence

And this is really important: Many women trying to lose fat are eating in a calorie deficit – and in a calorie deficit, your body is already much more likely to break down muscle.

So your job is very clear: Do everything you can to preserve it.

This is why exercise selection matters so much.

HIIT creates a strong “keep this muscle” signal through higher intensity and greater muscle recruitment.

LISS burns calories, but it does not protect your muscle tissue.

Interesting note: Participants in the LISS group reported higher levels of overall psychological well-being, likely because the slower, steady pace is more relaxing and less stressful.

Both have their place.

But if your goal is fat loss and maintaining or building muscle, HIIT should be your priority. You don’t need to eliminate LISS completely if you enjoy it, just don’t rely on it as your primary strategy.

Remember: the goal isn’t just to lose weight – it’s to build a strong, healthy, resilient body that looks, feels, and functions at its absolute best.

💪 If you’re tired of trying to navigate your health on your own, my 1:1 coaching program offers personalized nutrition and fitness coaching, ongoing accountability, and direct access to me for expert guidance, encouragement, and support every step of the way. Apply here.