TV doctor behind the 5:2 diet swallows a TAPEWORM in bid to lose weight for new documentary (but gains 2lbs)

  • Dr Michael Mosley infected himself with tapeworm cysts taken from cows
  • Victorian women swallowed them and they were thought to aid weightloss
  • Dr Mosely found he gained 2lbs after his cravings for chocolate increased
  • Beef tapeworm is safer than the dangerous pork tapeworm which moves


He is the man behind the popular 5:2 diet.

But despite championing the phenomenon known as The Fast Diet, Dr Michael Mosley has decided to try out another, historical way to shed the pounds – worms.

Well-known for self-experimentation, the science journalist infected himself with tapeworms – one of the most unpleasant parasites known to man.

Michael Mosley holding up a piece of human tapeworm

Parasite: Dr Michael Mosley holds up a tapeworm during his new programme. He infected himself with the tapeworm to see if he lost weight but he actually gained 2lbs after his appetite for carbohydrates increased

The results of his experiment will be broadcast during a new programme called Infested! Living With Parasites which will air on BBC4 next month as part of the corporation’s Natural History month.

The documentary follows Dr Mosley as he lives with the parasites in his guts for six weeks.

Historically tapeworms were thought to be a weight-loss aid, with Victorian women swallowing the parasites’ eggs in their quest to lose weight.

But Dr Mosley found he actually gained weight, adding 2lbs, during his stint as a human guinea pig.

He has also revealed that health and safety regulations meant the BBC cleared him to consume the tapeworms – which can grow up to 100ft in length in the intestines – but drew the line at him deliberately getting head lice, even though it affects millions of schoolchildren each year.

Living With Parasites: Dr Michael Mosley demonstrates tapeworm…



TV science presenter MICHAEL MOSLEY lived with tapeworms in his guts for six weeks for a documentary

Intestine: Dr Mosely realised there was a tapeworm (pictured) inside him when he swallowed a camera to allow him to see whether the cysts had transformed into tapeworms. He had three parasites in his gut

Dr Mosley said his weight gain could have been caused by the need to increase his food intake as a result of the parasites living in his guts.

‘I was keeping a food diary to see if my food preferences changed,’ he said.


A tapeworm is a parasite that can live in a person’s intestines.

They tend to be flat, segmented and ribbon-like.

Humans can catch them by touching contaminated faeces and then putting their hands near their mouth, swallowing contaminated food or water or by eating raw contaminated pork, beef or fish.

Many patients do not know they have a tapeworm infection until they see segments of the worm in their stools.

Symptoms include stomach pain, vomiting, diarrhoea, weight loss, malnutrition and changes in appetite.

A beef tapeworm, as swallowed by Dr Mosley, remains in the intestines and is easily treated with tablets.

Other tapeworms can cause serious problems as they can settle in other parts of the body.

Tapeworm infections are most common in developing countries – they are rare in the UK.

Source: NHS Choices

‘I think I probably ate a bit more chocolate. Tapeworms like beer and chocolate – they like carbohydrates.

‘My weight if anything went up a bit. One of the theories is that the tapeworm probably encourages you to eat more. You feed it.’

In order to infect himself with the tapeworm, Dr Mosley travelled to Kenya where his team tracked down the parasite, harvesting cysts from the tongue of an infected cow in an abattoir in Nairobi.

The cysts form in infected cattle and contain baby beef tapeworm, which can live for up to 20 years.

Dr Mosley swallowed three cysts. ‘It’s not something you can easily lay your hands on,’ he said.

‘My wife’s a GP and she was not very keen but she said it was OK because beef tapeworm is relatively innocuous. And also it is not infectious.’

Six weeks later, Dr Mosley swallowed a camera, to allow him to see whether the cysts had transformed into  tapeworms. Linked to his iPad, the camera revealed that Dr Mosley had  three parasites growing in his gut.

The beef tapeworm makes its home in the intestine and is safer than other  forms of the parasite. The pork tapeworm, in contrast, is far more  dangerous, moving around the body. They can cause brain cysts in humans.

Scientists have been increasingly fascinated by the effects of parasites on the  human body. It has become widely accepted that their eradication in most parts of the world has led to a rise in allergies and many other  conditions.

Historically tapeworms were thought to help people lose weight. But Dr Mosley's experiment revealed he gained 2lbs, the result, he suspects, of his increased appetite

Historically tapeworms were thought to help people lose weight. But Dr Mosley’s experiment revealed he gained 2lbs, the result, he suspects, of his increased appetite

‘I like finding out stuff through my personal experience of it,’ Dr Mosley said.

‘They get very few people who are  prepared to be infected by tapeworms. Hopefully my faeces will  contribute at some time in the future to a better test.

‘There was a time when Victorian ladies would swallow tapeworm eggs in the  hope that it would help them lose weight, but this was actually a  fallacy because the eggs are not infectious to human beings – they are  only really infectious to cattle.

‘It is part of the peculiar life-cycle  of the beef tapeworm that when you pass segments and eggs, they have to  be eaten by a cow before they become infectious.’

I like finding out stuff through my personal experience. They get very few people who are prepared to be infected by tapeworms. Hopefully my faeces will contribute at some time in the future to a better test’
– Dr Michael Mosley


Producer Nathan Williams said that BBC policies allowed Mosley to consume the tapeworm because it could not be passed from human to human, but parasites such as pinworm and head lice fell foul of guidelines.

However, he was allowed to experiment with the lice as long as they were placed on his arm.

‘It’s fine to eat a tapeworm but they wouldn’t let us have a pinworm even though 40 per cent of the children in the UK have it,’ Mr Williams said.

‘Similarly they wouldn’t let us give head lice in the hair because you might give it to other people and it wouldn’t be fair to infect Michael’s family and his friends.’

The tapeworms were killed off using pills, although the team had not been able to trace the bodies being expelled from Dr Mosley’s body.

He said: ‘Nothing came out. There are two possibilities: the most likely possibility is that the pills killed the worms and my body digested the tapeworms which is an ironic end – parasite gets eaten by its host, which is most likely.

‘The second possibility is they are still there, but since it is about 13 weeks since I swallowed the cysts, I think I would have noticed by now.’


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