Doubts on Safety of Intermittent Fasting Diets

• Intermittent fasting has become increasingly popular for people wanting to lose weight
• Experts are concerned about the effects IF has on blood sugar regulation and damage caused to cells by free radicals
• Evidence on the success of intermittent fasting is very contradictory and more studies are needed

Intermittent fasting has gained popularity recently and can help with rapid weight loss.

But it could also increase the risk of diabetes according to new data presented at the annual meeting of the European Society of Endocrinology.

However, the jury is still out.

The Data

Adult female rats were used for the data gathered. They were submitted to intermittent fasting for three months, with body weight and food intake being recorded.

The researchers were investigating whether intermittent fasting increased the risk of diabetes by impairing the action of sugar-regulating hormone, insulin and damage at cellular by free radicals produced by fasting.

The Results

Once the study was over, the results showed that, in the rats, intermittent fasting did indeed decrease body weight and food intake.

However, the rats’ stomach size had greatly increased as had the amount of fat tissue they had. They had also lost some muscle mass.

There was an elevation in insulin levels and an increase in insulin secretion in the pancreatic islets as well as an indication of insulin resistance.

One of the researchers, Ana Bonassa from the University of Sao Paulo, says,

'This is the first study to show that, despite weight loss, intermittent fasting diets may actually damage the pancreas and affect insulin function in normal healthy individuals, which could lead to diabetes and serious health issues.'

She does, however, acknowledge that more studies are needed, an opinion shared with other experts in nutrition and diabetes.

Expert Opinions

Dr Nicola Guess, Lecturer in Nutritional Sciences at King’s College London, said:

'Firstly, it’s important to bear in mind there are important differences between rodents and humans – particularly with regard to diet. For example, a high fat diet causes insulin resistance in rats but it does not appear to in humans.'

She went on to explain that if the rats had been fasted for 24 hours, that was the equivalent to a 3-4 week fast in humans.

Dr Simon Cork, Research Fellow in the Division of Diabetes, Endocrinology and Metabolism at Imperial College London, said:

'There are a few important caveats to this study.  The study was performed in rats, so more research is needed to understand whether these results are applicable in humans.'

He went on to say,

'The ‘diabetes’ was assessed by looking at markers associated with insulin resistance, which doesn’t actually mean that the animals had become diabetic; it points towards that possibility.'

The general consensus from these experts is that this one study is not cause for concern.

Mainly because of the differences between rodents and humans and because of the lack of studies backing up the results.

They all agreed that more studies were needed.

WLR says . . .

In previous studies, when compared to a Mediterranean diet, those people doing intermittent fasting didn’t fare any better in terms of weight loss.

That said, different approaches suit different people and for some, intermittent fasting may be the way forward.

But why deprive yourself of food on some days when the Mediterranean diet, for example, gives the same results?

Add to that the controversy surrounding intermittent fasting, I think I would leave it alone and opt for a healthy, sustainable, well-balanced diet and count my calories instead.