Australian evidence for benefits of time-restricted eating

Associate Professor Leonie Heilbron

South Australian-led research has found time-restricted eating (TRE) reduces body weight and fasting glucose and dampens energy-consuming pathways in adipose tissue.

The investigators, from the South Australian Health and Medical Research Institute (SAHMRI), said their findings provide “novel evidence that TRE could potentially be a therapeutic strategy for patients with obesity and prediabetes”.

The open-label, single arm study of 15 men aged 40-70 years, with a mean BMI 30.5 and waist circumference of 113cm, comprised 8 weeks of a largely self-selected 10-hour time window for eating, as long as meals were completed by 7.30 pm.

There were no other dietary instructions and participants were asked to maintain their usual level of physical activity and normal sleep patterns,

The study, published in Nutrition, found the intervention led to a modest reduction in the eating time window from 14.6 to 10.6 hours. The estimated average daily energy intake was not significantly changed by the intervention.

Participants demonstrated a significant reduction in body weight (P=0.015), waist circumference (P=0.014), visceral fat mass (P=0.020), percent body fat (P=0.010), fasting plasma glucose (P=0.026) and HbA1c (P=0.008) from baseline.

There was no change in blood pressure, fasting insulin, total cholesterol, HDL-C, triglycerides, or non-esterified fatty acids (all P>0.05).

“TRE did not significantly reduce breakfast glucose AUC (-0.25 ± 0.16mmol/L/h, P=0.131) and increased the dinner glucose AUC (0.51 ± 0.11mmol/L/h, P<0.001),” the study authors said.

“There were no significant effects of TRE or mealtime on pre-meal and postprandial insulin.”

The study also found TRE was likely to be sustainable given it reduced pre-meal desire to eat, hunger, prospective consumption (how much food participants thought they could eat) and increased feelings of pre-meal and post-prandial fullness.

“Interestingly, altered subjective appetite feeling in response to TRE may induce a shift in preference to eat earlier in the day, which could promote weight loss and glycaemic control.”

“However, there was no detectable effect on postprandial ghrelin or GLP-1, but GIP was elevated by TRE.”

The study also found transcriptional changes in biopsied subcutaneous adipose tissue with downregulation of key genes in mitochondrial biogenesis and oxidative phosphorylation.

“In particular, genes encoding subunits of mito-ribosome (MRPS35, MRPL33, MRPL51), mitochondrial ribosome proteins translocation (TOMM7, TOMM 22), and the electron transport chain and ATP synthase (NDUFA12, NDUFS5, ATP5F1E, ATP5PD).”

“Whilst changes in mitochondrial biogenesis and oxidative phosphorylation in humans in response to TRE has not been previously evaluated, caloric restriction and fasting is known to attenuate pathways involved in oxidative phosphorylation in adipose tissue.”

“Potentially, this could reduce mitochondrial reactive oxygen species production, and slow ageing,” the authors said.

Simple message

Senior investigator Associate Professor Leonie Heilbronn, who leads the Obesity and Metabolism laboratory at SAHMRI, told the limbic that TRE was a simple message to convey to patients.

“TRE is a nice simple message and we are seeing that clinicians like to provide diet advice to their patients but they really don’t have the time to be sitting there giving them all that information.”

“We don’t have all the evidence yet but it looks like it is improving health and it is reducing disease risk.”

She said it was unclear how short the fasting period should be to generate health benefits.

“The only study done in comparison was between 4 hours a day and 6 hours a day and either 4 or 6 hours both produced health benefits. We were trying to do an intervention that was a bit more sustainable than 6 hours of TRE for every day for the rest of your life. We were interested in something that was a bit more flexible.”

Associate Professor Heilbronn said all of the men in the study chose 9am-7pm for their eating period.

“What we saw was that similar pathways were activated to what we see with a caloric-restricted diet.”

She said trials were underway comparing caloric restriction with TRE and also whether the combination might generate additive effects.

A multicentre trial was currently recruiting people at high risk of diabetes to compare usual dietetic practice with TRE advice and following participants over 12 months.

As well, studies of TRE in people with diabetes were coming.

“I suspect it will also work in people with diabetes but those who are insulin or the sulfonylureas possibly need to be more careful. They would need to be a lot more careful but people who are on metformin or the newer generation of drugs that don’t cause hypoglycaemia.” she said.

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