Fasting appears to do more than simply help you lose weight, with research suggesting it could help you to live longer.
United States and Italian researchers found people who followed a low-calorie low-protein diet, which aimed to mimic fasting for five days a month for three months had a decrease in risk factors associated with chronic diseases such as cancer, heart disease and type 2 diabetes.
Many of us are familiar with the concept of intermittent fasting, where you significantly reduce the amount of energy (kilojoules) you consume one or two days per week, as a tool for weight loss.
Advocates have also argued it can help you live longer and ward off disease, but until now most of the evidence for fasting diets has come from studies of mice.
For the new study, just published in the journal Cell Metabolism, researchers followed 34 people, 19 followed the Fasting Mimicking Diet (FMD) and the rest just ate a regular diet.
It’s not a magic formula for weight loss and longevity so you don’t need to think, ‘how can I get my hands on this formula?’
Associate Professor Amanda Salis
By the end of the three months those who followed the diet had not only lost weight, but had lower blood sugar levels and reduced markers for heart disease.
Professor Valter Longo, one of the study’s authors, said a fasting diet is one that is “complex and designed based on its ability to provide calories without triggering pro-aging pathways”.
The researchers undertook the human study after their initial mouse research found the animals lived longer and experienced cell regeneration.
So, you want to fast too?
Does this mean intermittent fasting is going to keep us trim and give us extra years of good health?
“I think fasting diets like the 5:2 can be beneficial but when we compare its effects to the FMD, it has several disadvantages and some advantages,” Professor Longo said.
He said the 5:2 fast requires a person to severely modify their diet every few days, which he argues can affect metabolism and sleep patterns.
It also requires twice as much calorie restriction per month and it does not affect some cancer or ageing markers, like the FMD can.
On the plus side, it does require less medical supervision than the FMD.
Associate Professor Amanda Salis of the University of Sydney’s Boden Institute of Obesity, Nutrition, Exercise and Eating was circumspect about the findings of the report.
“The important thing to note is that this is not a magic formula for weight loss and longevity, so you don’t need to think, ‘how can I get my hands on this formula?'” she said.
“The diet is effectively like eating very little — about 3,000 kilojoules per day — and taking appropriate supplements for five days out of every month, which we know will result in weight loss and improve health in many people, at least over a time frame of six to 12 months.”
She said anyone interested in exploring intermittent fasting-type diets should visit their GP.
“Generally speaking, any time you alter your diet or exercise regime, always get the all-clear from your GP, because there are some people for whom intermittent fasting — or other interventions — are not suitable,” she said.
Good news for mice, jury still out for humans
“I think the findings [of the study] for mice are very encouraging because the verdict has been out as to whether intermittent energy restriction prolongs life, as is the case for continuous energy restriction in some, but not all, strains of mice and in smaller creatures, like insects,” Associate Professor Salis said.
“For mice, this study really does show that long-term intermittent fasting not only reduces body fat levels, but also improves immune and cognitive functions, reduces tumour growth and reduces cardiovascular disease and diabetes as well as prolonging life.
“It is a very thorough investigation of all these parameters. It is a very elegant study.
“But for humans, the verdict is still out.”
While this initial research is promising, Professor Longo and his team remain cautious and say a larger randomised clinical trial still needs to be undertaken to confirm their findings.
Associate Professor Amanda Salis is seeking post-menopausal women, aged 44–65 years, from the Sydney metropolitan area for clinical weight loss trials in 2015 and onwards. For more information, contact her team at: tempo.diet@sydney.edu.au