High-intensity interval training — think quick sets of burpees and squat jumps — has been gaining popularity in the fitness arena for decades.
And time-restricted meals, which people may find less tedious than counting calories, have garnered attention for almost as long.
But new search finds that when overweight women combine the two approaches, they can achieve an unexpected improvement in their health.
The study followed more than 130 sedentary, overweight women for seven weeks, dividing them into four groups. A control group did no different.
One group did three 35-minute HIIT workouts each week. The researchers supervised the exercise sessions, making sure the participants were working hard enough to reach 90% of their maximum heart rate.
A third group used a time-restricted food approach, consuming all of their calories within a 10-hour window. (For example, they only ate between 10 a.m. and 8 p.m.)
A fourth group added HIIT workouts and time-restricted eating.
The exercise-only, diet-restricted groups saw health gains, including a reduction in fat mass and visceral fat.
But the group that did both – exercise and restricted diet – made more dramatic changes, losing twice as much fat. And they did much better at improving their long-term glycemic control.
The combination of a diet and exercise program seemed more appealing than either approach on its own.
This is great news for the tens of millions of women struggling with their weight and health, said Jessica Corwin, registered dietitian at Corewell Health’s Women’s Health & Wellness Center.
“It’s especially important for women going through perimenopause and menopause,” she said. “That’s when their weight increases, and for many their sugar levels hit the danger zone.”
It is particularly exciting that the study focuses entirely on women.
“It’s pretty rare in randomized controlled trials,” she said.
Make HIIT work for you
Words like “high intensity” are likely to scare off gym-o-phobes. But Corwin is quick to point out that it’s all relative.
“You train very hard, but only for brief periods,” she said. “And that intensity is measured against your heart rate, not an elite athlete.”
While there are nearly endless variations, the basic principle remains: quick bursts of hard work raise your heart rate. Shorter rest periods allow your heart rate to slow down.
This may mean sprinting from telephone pole to telephone pole on your morning walk, then walking, then running again.
In the gym, this may mean short bursts of jumping jacks or squat jumps, followed by very brief rest intervals.
“There’s no need to try to run a six-minute mile,” she said.
Hard and sweaty? Yes. But the joy, she says, is that it’s only 30 minutes, three times a week.
“There’s no need to spend hours in the gym if you don’t like it,” she said.
“And plenty of research shows that even shorter HIIT workouts, some as quick as 15 minutes, are beneficial. You can really get your heart rate up.
One caveat, she said, is that for many women with Hashimoto’s disease or other thyroid issues, HIIT can be problematic.
“It can tax the adrenal glands and make weight loss more difficult,” she said.
Not sure about the condition of your thyroid?
“It’s a good idea to ask your provider for a full workup at your next checkup, especially if you’re having issues with weight gain or fatigue,” Corwin says.
Time-limited eating
A 10-hour eating window is “pretty realistic,” Corwin said.
Start with time-restricted eating by choosing a time window that most easily fits your lifestyle.
People are often unaware of the amount of grazing they do all day and all evening, often without feeling satisfied.
The shorter time window often allows you to focus on three best meals each day, with 20-30 grams of protein at each of those meals.
“There’s so much evidence that getting enough protein increases satiety, wards off those sweet cravings later in the day, and keeps us energized throughout the day,” Corwin says.
With those solid meals under your belt, “it’s easy to stop eating at 7 p.m. and not eat again until 9 a.m. the next day,” she said. “And even going from 7 p.m. to 7 a.m. is an incredible start.”
Black coffee and tea are fine.
“But keep in mind that adding anything, even a calorie-free sweetener like Stevia or Splenda, breaks the fast,” Corwin says. “It tells your body something sweet is coming and it starts producing insulin.”
The key: Adjust the window to suit your life, whether cooking for a family or working different shifts.
Another reason it works so well, she says, is that it’s very forgiving.
“So maybe one night you go out to dinner in front of that window or have a glass of wine later in the evening,” she said. “Just reset the clock and start again the next day.”
Although the research study looked at the impact of this eating style on metabolic health, “it also helps fight heartburn, which is a big problem for many women,” Corwin said. .
Plus, she loves how it encourages women to listen to their bodies differently, promoting a more mindful and intuitive approach to nutrition.
“You can say, ‘I’ve always been a big breakfast person,’ and then find out that you like to wait until 10 a.m.,” she said. “And our bodies are different every day, especially for women with a menstrual cycle.
“For many, it helps them get in touch with what their body is saying and what they crave.”
