Despite the $255 billion global diet industry and £2 billion in the UK, objective research shows widespread agreement that diets don’t work. “I would agree with that,” says Trine Balsvik, “Eating less, focusing only on calories is the worst, depressing, irritating. Completely unhappy. This is not life.”
Trine Balsvik lives in the small village of Hell in central Norway with her partner and one of their two adult daughters. Now, at 45, she says, “I’ve tried many weight-loss diets without success.”
Balsvik weighed 80 kilograms when she read about the new study, which involved recruiting participants for a seven-week study that combined time-restricted eating (TRE) and high-intensity interval training (HIIT). “I like being involved in scientific research, but this one really drew me in. I wanted to lose weight.”
In a seven-week randomized controlled trial, 131 overweight or obese women of reproductive age with an average age of 36 years were divided into four groups. One does TRE alone, limiting energy intake to no more than a 10-hour “eating window” throughout the day starting no later than 10 a.m., the other does HIIT consisting of supervised treadmill running sessions three times a week, the third does a combination TRE and HIIT and a control group that did nothing.
Outside of time constraints, participants were asked to eat and drink as usual. Participants were advised to open the feeding window no later than 10 am.
In a collaboration between Norwegian and Australian authors, the study, which was published last October in Cell Metabolism, showed improvements in many key biomarkers in all but the control group, including a significant improvement in blood sugar response and a reduction in visceral “belly fat,” which indicates an increased risk of cardio-metabolic disorders such as heart disease and type 2 diabetes.
Balsvik was part of the TREHIIT group, which, as might be expected, was doing the best. Balsvik lost half a stone (three kilograms) in seven weeks, her BMI dropped from 29.5 to 28.5, and she lost almost 20 cm of visceral “belly” fat, which was quite average for her group.
She says the hardest thing about the study was the 30-minute journey to exercise sessions and the impact of running on her hips and knees. Plus, she says it was “easy.”
And this is where this little study is interesting. Easy? The word rarely appears in the same sentence as “diet.” While HIIT has been an effective intervention, Balsvik has not pursued it since the study ended two years ago, but she still has enthusiasm for TRE, which she found easy.
“I was very anxious before I started. You wonder, “How am I supposed to do my job if I haven’t eaten?” I felt hungry for about two days, but not extreme, and then my body got used to the routine, I had more energy, and I was in a great mood. It was the complete opposite of what I expected.”
After the study, she continued TRE, losing another four kilograms and 12 cm of visceral fat (abdominal fat around the organs in the abdomen). “I’m sticking to it. Sometimes we eat a little later in the evening on the weekend and my body reacts and I feel sick like there’s something wrong with me. Now my boyfriend has joined me.” Didn’t notice any significant improvement. “I think his feeding window is too long, 13 hours and too late.”
One of the authors of the study, Kamilla Haganes from the Department of Circulatory and Medical Imaging at the Norwegian University of Science and Technology, says TRE should not be confused with intermittent fasting because it is a “nutrition chronostrategy.”
Popular fasting regimes such as 16:8, 5:2 or OMAD (one meal a day) “are mainly related to the energy restriction achieved with intermittent fasting periods. In contrast, TRE’s emphasis is primarily on shifting energy intake to those parts of the day when the human body is physiologically ready to digest and use energy.”
How TR works
TRE works in harmony with our circadian rhythms, the body, brain, and even individual cells and genes all have their own clocks that run roughly in sync with the 24-hour day. Food and light activate certain functions. Sleep, body temperature, hormone levels, and digestion all depend on these natural, fairly rigid circadian rhythms in all humans.
One very famous study turned many self-identifying “night owl” students back to natural “larks” in a matter of days, simply by taking away all artificial light sources at night.
Another study found that even when there is no weight loss, TRE still improves metabolic markers in men with prediabetes. Balsvik is now effortlessly over a stone lighter in two years, with a BMI of 27 and significantly reduced visceral fat after cutting back on ultra-processed foods and increasing protein and vegetable choices.
She plans to revive her HIIT regime with exercises that are easier on her knees. Exercise will help, he says, but “If you’re not a naturally motivated person, you need encouragement…” Many of us will understand the sentiment.
One study last summer found that TRE is most effective between the hours of 7am and 3pm. Another found that those who stick to TRE but eat later dinner see less benefit.
So eat your evening meal early. Your body will thank you.