Researchers studying TRE (time restricted eating) ran a seven-week randomised controlled trial with 131 overweight or obese participants in Norway last year.
Researchers studying TRE (time restricted eating) ran a seven-week randomised controlled trial with 131 overweight or obese participants in Norway last year.
Despite the US$255 billion (NZ$346b) global diet industry, objective studies show broad agreement that diets don’t work.
“I would agree with that,” says Trine Balsvik, “Eating less, focusing only on calories, it’s the worst; depressing, infuriating. Totally miserable. That’s not a life.”
Trine Balsvik lives in a small village calledHell in the middle of Norway with her partner and one of her two grown-up daughters. Now 45, she says, “I have tried many weight loss diets with no success.”
Balsvik weighed 80 kilograms when she read about a new study that was recruiting subjects for a seven-week trial combining time-restricted eating (TRE) and high-intensity interval training (HIIT): “I like contributing to scientific research, but this one really attracted me. I wanted to lose weight.”
The seven-week randomised controlled trial split 131 overweight or obese women with an average age of 36 into four groups. One doing TRE alone, restricting their energy intake to no more than a 10-hour daytime ‘eating window’, beginning no later than 10am; the second doing HIIT, consisting of supervised treadmill running sessions three times a week; a third doing a combination of TRE and HIIT; and a control group that did nothing.
Other than time restrictions, the participants were asked to eat and drink as they would normally.
A collaboration between Norwegian and Australian authors, the study, which was published in Cell Metabolism last October, saw improvements in a number of crucial biomarkers in all the groups except the control, including a wide improvement in blood sugar reactions and a reduction in visceral fat (belly fat around organs in the abdominal cavity), which indicates a raised risk of cardio metabolic disorders like heart disease and Type 2 diabetes.
Balsvik was part of the TRE / HIIT group, which, unsurprisingly, did best. Balsvik lost half a stone (3kg) in seven weeks, her BMI dropped from 29.5 to 28.5 and she lost nearly 20cm of visceral belly fat, which was pretty average within her group.
She says the hardest thing about the study was the 30 minutes of travel to the exercise sessions and the impact running had on her hips and knees. Other than that she says it was “easy”.
Sleep, body temperature, hormone levels and digestion are all affected by our circadian rhythms. Photo / Lux Graves, Unsplash
Minimal effort
And here is where this small study is interesting. Easy? The word is rarely seen in the same sentence as diet. While the HIIT was a successful intervention, Balsvik has not kept it up since the study ended two years ago, but she’s still enthusiastic about TRE, which she found effortless.
“I was very anxious before I started. Wondering ‘how am I going to do my work if I haven’t eaten anything?’ For two or so days I had this sense of hunger but not extreme and then my body liked the routine, I had more energy and was in a great mood. It was the complete opposite to what I expected.”
After the study she continued following TRE, losing a further 4kg and 12cm of visceral fat. “I stick to it. Sometimes we eat a bit later in the evening at the weekend and my body reacts and I feel sick, like something is wrong with me. My boyfriend has joined me on it now.” He has not seen significant improvements - “I think his eating window is too long, at 13 hours, and too late,” Balsvik says.
One of the study’s authors, Kamilla Haganes of the Department of Circulation and Medical Imaging at the Norwegian University of Science and Technology, says TRE should not be confused with intermittent fasting because it is a “chrono nutritional strategy”.
Popular fasting regimes such as 16:8, 5:2 or OMAD (one meal a day) “are mainly linked to the energy restriction achieved with intermittent periods of fasting. In contrast, TRE primarily emphasises shifting energy intake to parts of the day where the human body is physiologically prepared to digest and utilise energy.”
TRE and circadian rhythms
TRE works in harmony with our circadian rhythms. The body, brain and even individual cells have their own clocks that work roughly in synch with the 24-hour day. Food and light switch certain functions on. Sleep, body temperature, hormone levels and digestion are all affected by these natural, fairly inflexible circadian rhythms across all human beings.
One study last summer found TRE most effective when implemented between 7am and 3pm. Another study found that those who stick to TRE but eat a later dinner see fewer benefits. Another found that even if there is no weight loss, TRE improves metabolic markers in pre-diabetic men.
Balsvik is now over a stone lighter two years on, with a BMI of 27, and greatly reduced visceral fat, having cut down on ultra-processed foods and increased protein and vegetables out of choice.
She plans to resurrect the HIIT regime with exercise that’s easier on her knees. The exercise will help, she says, but “unless you are a naturally motivated person, you need encouragement…”
How TRE works
Eat and drink normally within a fixed eight- to 12-hour window every day, starting at breakfast.
Once your eating window closes, do not eat or drink anything except water, black tea or coffee (although that could play havoc with sleep).
If you’re having a night out, enjoy it without self-recrimination. Get back to your regular eating window the next day.
If your schedule is unpredictable and you find eating inside the window is difficult, TRE is probably not for you.
