Does Cardio Cause Muscle Loss?

Does Cardio Cause Muscle Loss?

Ram Karri


It's nearly beach time – ready to show off those Abs? If not, then the chances are you're frantically considering upping your cardio and hitting the spin classes. However, no doubt you're also concerned by one of the biggest questions asked by gym trainers; does cardio cause muscle loss?


Back in 1999 scientists studied the impact of cardio on muscle loss – they put dieters on a 800kcal diet for 12 weeks, combined with either 4 hours of cardio (running or biking) or 3 weight training sessions weekly.

Both groups lost a similar amount of weight – but crucially, the cardio group lost a lot of muscle tissue, while weight trainers maintained lean mass, incinerated body and and increased their metabolic rate <1>!

Although an 800 calorie diet is way too low for any guy to sustain, it demonstrates that weight training and an energy controlled nutrition plan (with sufficient protein) is highly effective for getting ripped. Equally – cardio can cause muscle loss if you're not careful!


You can still use cardio to boost the 6-pack impact of a weight training plan and calorie controlled diet. The secret is high intensity interval training which has been shown to stimulate the loss of abdominal fat <2> while protecting muscle, especially when combined with a high protein diet which is proven to have muscle-protective impact <3>.

Examples of HIIT cardio sessions:

100-200m sprints followed by 4 mins rest. Repeat 6 times. 1 min high intensity followed by 30-60 secs low intensity for 30 minutes 100m sprint (rest 2 minutes), 200m sprint (rest 3 minutes), 400m sprint

Effective weekly strategy:

3 x weights sessions 2 HIIT sessions Calorie deficit 500kcals daily (from exercise and diet!) Protein intake 2g/protein/kg body mass Never do cardio to create a massive energy deficit!

Regardless of your choice of cardio, always supplement with BCAA's before/during training, followed by a protein shake post-workout, to ensure your cardio doesn't cause muscle loss.


<1> J Am Coll Nutr. 1999 Apr;18(2):115-21. Effects of resistance vs. aerobic training combined with an 800 calorie liquid diet on lean body mass and resting metabolic rate.

<2> J Obes. 2011; 2011: 868305. High-Intensity Intermittent Exercise and Fat Loss

<3>S. M. Pasiakos, J. J. et al. Effects of high-protein diets on fat-free mass and muscle protein synthesis following weight loss: a randomized controlled trial. The FASEB Journal, 2013; 27 (9): 3837 DOI: 10.1096/fj.13-230227


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