It sounds too good to be true – you can burn calories and lose weight, even while you sleep.
Yet, a team of scientists have discovered for a lucky group of people, that dream is a reality.
They found the burning of calories overnight is driven by the microbes in our gut, reports Daily Mail.
The team, from the University of Iowa, determined unhealthy changes to gut bacteria can trigger weight gain.
They hope their findings will lead to new treatments for obesity.
Study author Dr John Kirby, a professor of microbiology and urology, said: ‘Our research leads to the conclusion that it is probably bacteria (in the gut) that are responsible for the calories you burn while you are asleep. ‘
Dr Kirby and a team of researchers focused their study on the effects of risperidone – an antipsychotic drug that causes ‘significant weight gain’ in patients.
Risperidone is used to treat psychiatric disorders in adults and children, such as autism, bipolar disorder and schizophrenia.
Prescription rates for risperidone have ‘increased nearly eight-fold over the last two decades’.
Dr Kirby and a colleague determined in an earlier study that patients taking risperidone in the long-term gained weight because of a significant shift in the composition in their gut microbiomes.
In the new study, the researchers sought to explain how this risperidone-induced microbiome shift causes weight gain.
They found that risperidone causes weight gain in mice – an extra 2.5 grams, or nearly 10 per cent of the total body mass – over two months.
Researchers also determined that the drug significantly alters the bacterial composition of the mice microbiome.
The altered microbiome was found to cause a reduction in the resting metabolic rate ‘that is entirely responsible’ for the weight gain.
Dr Kirby said: ‘The control mice gain a little weight as they age and their microbiome undergoes a “healthy shift” due to aging.
‘With the risperidone, the mice become obese and exhibit an alternative, less healthy shift in their microbiome.
‘With this study, we now have a mechanism for how a shift in the microbiome contributes to weight gain, and it’s to do with changes to the resting metabolic rate.’
The team used a total calorimetry machine to take precise measurements of the mice energy intake, oxygen consumption and carbon dioxide output and heat production.
That allowed them to determine the total energy change – or delta G – of the mouse.
Researchers found there was no change in aerobic – or oxygen-dependent – resting metabolic rate for mice fed risperidone, as compared to the control mice.
However, there was a decrease in non-aerobic resting metabolic rate that could account for the animal’s weight gain.
Study co-author, Dr Justin Grobe, an assistant professor of pharmacology, said: ‘It’s about a 16 per cent change in resting metabolic rate, which is enormous.
‘It would be 29 pounds of fat gained every year for an average human.’
Dr Kirby added: ‘That is the equivalent of eating one additional cheeseburger every day.’
The researchers then sought to prove that it was the ‘shift’ in microbiome that is responsible for metabolic change and weight gain.
They transferred the microbiome from risperidone-fed mice into control mice and saw the same effect.
Furthermore, they found it wasn’t just the bacteria that produced that effect.
The transfer alone of a bacteriophage (phage) – which is a type of virus that infect microbiome bacteria – was ‘sufficient to reduce resting metabolic rate and cause weight gain’ in the control mice.
As a result the study suggests that manipulating the resting metabolic rate – specifically by targeting the gut microbiome – could be a new approach to treating obesity.
The researchers also suggest that preventing unhealthy changes to the microbiome may prove beneficial for patients taking risperidone.
The study was published in eBiomedicine.