What is the intermittent energy restriction diet, and is it safe for weight loss?

New research suggests it improves brain function and gut health, but may not be suitable for all

IER involves eating in caloric deficit for a few days, followed by eating at caloric maintenance for a few days. Photo: Farhad Ibrahimzade / Unsplash

Losing weight, getting fit and generally leading a healthier life, is perhaps the most common New Year resolution. Some people work out more, others take on a sport, while some go down the eating healthy route.

While the Mediterranean diet often comes out on top, new research suggests intermittent energy restriction could be just the ticket for some.

How does intermittent energy restriction work?

IER involves alternating periods of eating in caloric deficit interspersed with periods of eating at caloric maintenance.

For example, a person could restrict calories by 30 per cent below maintenance for two weeks, then spend the following two weeks eating regularly.

This is a modification to most diets that promote continuous caloric deficit in order to achieve weight loss goals. One of the USPs of this approach is to avoid an impending diet crash, which is what usually happens to people who drastically alter their eating habits to follow a strict deficit over the long term.

“IER works on the principle that intermittent periods of energy restriction may induce various physiological responses in the body, leading to improved metabolic health,” says Janani Satchithanantham, a specialist dietitian at Aster Hospital in Al Qusais, Dubai.

“During the fasting or reduced calorie periods, the body experiences changes in insulin sensitivity, cellular repair processes and hormone levels, all of which contribute to potential health benefits.”

Good bacteria, bad bacteria

Research published last week in the Frontiers in Cellular and Infection Microbiology journal, looked at how the gut microbiome and brain activity changed in a sample group with obesity (with a body mass index between 28 and 45) when put on the IER diet.

By the end of the study, the participants' weight decreased by an average of 7.6kg, or about 7.8 per cent. Researchers also noticed positive activity in brain regions associated with appetite and addiction regulation.

The results also pointed to increases in healthy gut bacteria including faecalibacterium prausnitzii, parabacteroides distasonis, and bacteroides uniformis. These microbes are associated with brain regions that control attention, motor inhibition, emotion and learning.

The study further noted a decrease in E coli, which is associated with dietary behaviour and people's willingness to lose weight.

Is IER safe?

As with other dieting methods, researchers suggest the effect is greater when the diet is followed consistently. “Long-term dietary intervention exerts a sustained impact on gut microbiota, whereas short-term dietary change only causes rapid and temporary changes in gut microbiota,” they write. “Thus, for weight loss maintenance, a highly controlled long-term IER intervention is recommended.”

However, Satchithanantham says people should exercise caution before embarking on any dieting strategy, and that IER “may not be suitable or safe for everyone”.

It is not advised for those with type 1 or type 2 diabetes, for example.

“Individualised approaches that consider personal health goals and potential risks are essential for a balanced and sustainable approach to dietary practices,” she explains.

She agrees, however, that the “current body of evidence suggests it holds promise as a viable approach for weight management and overall health improvement”.

For those who want to try IER, the Dubai specialist warns it is important to choose nutrient-dense foods instead of blindly monitoring caloric intake.

These food choices are crucial when it comes to the method's efficacy, she says, as they ensure the body receives the essential vitamins and minerals for a better health outcome.