Can Muscle really turn into fat?

Fortunately, the answer is no

So why did Arnold Schwarzenegger’s muscular body become replaced with a more fat and frail body?

  • Sarcopenia is when your muscles degenerate over time past the age of 50
    Click on image for more info

This is down to 2 things, firstly there’s something called sarcopenia where your muscles will degenerate by 0.5-1% each year when you’re past the age of 50. Arnold is now 69, so has potentially lost 19% of his muscle mass!

Particular omega 3 fatty acids (found in fish oils) have shown potential in slowing this effect. Additionally, maintaining exercise will result further building of muscle to replace the muscle cells lost.

Unfortunately, lowered testosterone levels in men over 50 will make this slightly more difficult.

The second factor is that Arnold would have had a high-energy demanding diet because of his high energy lifestyle when he was younger. As he adopts a more relaxed lifestyle in old age, but may continue to consume a high-energy diet. This results in excess calories that are then converted to fat

  •  The best way to avoid slowing of metabolism is to maintain aerobic exercises (e.g. running, cycling) and resistance training of muscles into old age
    Click on image for more info

As the ratio of his bodily muscle decreases and bodily fat increases, this results in a lower basal metabolic rate which is sometimes referred to as the “slowing of his metabolism”

The best way to avoid this is to maintain aerobic exercise (e.g. running, cycling) and resistance training of muscles into old age, and don’t use this myth as an excuse not to exercise!


Sam Fitzpatrick Final Year Medical Student, Cardiff University.

Milad Rouf Final Year Medical Student, Cardiff University.

Phillips SM (July 2015). "Nutritional supplements in support of resistance exercise to counter age-related sarcopenia". Adv. Nutr. 6 (4): 452–460. PMC 4496741. PMID 26178029. doi:10.3945/an.115.008367.

Gray, S.R. and Da Boit, M. (2013) Fish oils and their potential in the treatment of sarcopenia. Journal of Frailty and Aging, 2(4), pp. 211-216.

Johnstone AM, Murison SD, Duncan JS, Rance KA, Speakman JR, Koh YO (2005). "Factors influencing variation in basal metabolic rate include fat-free mass, fat mass, age, and circulating thyroxine but not sex, circulating leptin, or triiodothyronine". American Journal of Clinical Nutrition. 82 (5): 941–948. PMID 16280423.