Does Botox Cause Muscles to Weaken?

Lorna Jackson
By Lorna Jackson

Lorna was Editor of Consulting Room (, the UK's largest aesthetic information website, from 2003 to 2021.

Last week saw the pre-publication of a study by researchers at the Faculty of Kinesiology at the University of Calgary in Canada in which questions were raised about the therapeutic use of botulinum toxin type A (BTX-A).

As well as being used for cosmetic indications to treat lines and wrinkles, BTX-A is also used to treat a number of medical conditions such as cervical dystonia (a movement disorder which causes the muscles in the neck to contort) and spasticity in children such as that caused by cerebral palsy.

The Canadian study, to be published in The Journal of Biomechanics, found that rabbits injected with the Botox® brand of BTX-A experienced muscle weakness in muscles throughout their body, even though areas were far removed from the injection site.

The study also noted that repeated injection induced muscle atrophy and loss of contractile tissue on the limb that was not injected with the Botox. Many other mainstream media sources reported the sensational headlines that ‘Botox turns muscles to fat’, which will undoubtedly cause the public at large to speculate on the long term benefits of the use of Botox, no matter what the indication.

Are Botox treatments dangerous?

The lead author of the paper, Rafael Fortuna commented; “We were surprised by the degree of muscle loss and atrophy in the limb that was not injected with the Botulinum toxin. I think it's fair to say that the paper raises some important questions about the long-term therapeutic use of Botox, especially with children and adolescents."

The researchers used dosages that approximated the therapeutic doses used to treat spasticity and similar conditions in humans.

We asked Dr. David Eccleston, Clinical Director of Medizen Ltd, Medical Adviser to and experienced botulinum toxin clinical investigator what he thought of the publication of this study. He said;

“I was interested to read this article on the apparent new finding that Botox can cause muscle wasting elsewhere. It should be noted that the doses used in these animal studies, though claimed to be 'approximate' to those used therapeutically in humans, cannot be assumed to have the same effect in humans just by extrapolation. Many things are toxic to one animal species and not to another.

However, even if this were not the case, the doses of botulinum toxins such as Botox® used therapeutically are on average 10 times higher than those used in cosmetic practice, and in over 20 years of use there has not been one shred of convincing evidence in humans of any significant effect on muscles outside the injected area.

The assumption that there is somehow a 'danger' that has just been revealed is erroneous at best and negligent at worst, as this drug has so many uses in the treatment of things outside cosmetic use. The scare tactics spread by the less well-informed and more sensationalist parts of the media will do more harm than good by putting off patients from having treatment for such distressing and disabling conditions as chronic neuropathic pain, migraine, cerebral palsy and stroke.

Does Botox Cause Muscles to Waste away

The concept that muscles can 'turn to fat' is wrong. Of course if a muscle is relaxed by using a botulinum toxin it cannot 'work out' and any muscle that is not used becomes weaker and smaller, but it cannot be turned into another tissue type.

Perhaps the most important point to be acknowledged here is the need to ensure that if you are having treatment with Botox or similar, that it is done by a doctor in a properly registered clinic or hospital, and not behind a curtain in a beauty salon by an unqualified and inexperienced person, even if you do save a few pounds. Let the buyer beware!”

If you want to read more, the experts at Consulting Room really know what they're talking about and have put together Who should you trust to do your botox?Botulinum ToxinBotoxAzzalureDysportBocoutureXeomin and also lines and wrinkles FAQs just for you. 

If you have more questions, you can use the Botulinum ToxinBotoxAzzalureDysportBocoutureXeomin and also lines and wrinkles questions feature to talk to our panel of trained medical experts. 

If you're keen to get started with any of these treatments right away then you're in luck - those clever folks also have a list of trusted, accredited Botulinum ToxinBotoxAzzalureDysportBocoutureXeomin and also line and wrinkle clinics in your area.

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