It's a question we all ask ourselves at some point -- usually while wishing we could eat all the pizza in the world and not gain weight:
"Is there a way I can lose weight without having to diet or necessarily eat less?"
Well, it looks like there may be.
Evelyn Parr is a post doctoral research fellow from the Mary MacKillop Institute for Health Research at Australian Catholic University, who is leading a human study exploring how the timing of when we eat influences our health and weight.
This approach to eating is called 'time-restricted feeding', which you may associate with the hugely popular 5:2 diet.
"Time-restricted feeding is a bit different to 5:2 in the sense that the 5:2 diet is looking at five days of normal eating and two days of quite restricted feeding (consuming very low calories)," Parr told HuffPost Australia.
"What we're looking at is time-restricted feeding -- not necessarily reducing calories but reducing the time that you're consuming the food.
"Technically, you can have the same food but just over a shorter time window."
What this means is that the time between our last meal at night and our first meal in the morning is extended. For instance, instead of having your first meal at 7am and your last at 11pm (which is pretty standard as we eat food and work around the clock), having your first meal at 10am and last at 7pm.
"When you think about when you eat during the day, I know myself, I start eating early and sometimes finish late. This means the time window when I'm considered fasting -- which is defined as typically more than six hours -- is very short," Parr said.
If you're snacking until midnight and then up at six or seven o'clock, then you're almost not fasting -- ever.
"If you've got a population of people that are consuming unhealthy foods and you've got somebody who's also not moving a lot, we think their timing of eating and lack of fasting could be quite important.
"And this could potentially be modified without really needing to, say, 'ban' carbs or stop drinking all alcohol."
Sounds too good to be true? Let's take a look at the evidence and science behind time-restricted feeding.
Humans have a natural body clock, which is set by sleeping patterns, temperature, physical activity, our diets and when we eat. It's hypothesised that disruptions to our body clocks (in this case, eating late) can be detrimental to our health and contribute to diseases like obesity and diabetes.
"Researchers have done a lot of work in animals in terms of reducing the time that's available where they can access food, and found better metabolic profiles when the time of consuming food is shorter," Parr said.
"There has been one study that's looked at this reasonably short term in humans, using an iPhone app to get people to take photos of their food. They found that people were generally eating for 12-14 hours of the day.
"From their big cohort they then took a selected portion of those who were overweight but otherwise healthy, and instructed them to eat for 10-12 hours of the day instead. They didn't say anything about calories, macronutrients or other recommendations."
And the results showed that reducing the daily eating duration can contribute to weight loss.
"We're looking at an eight-hour time window with our humans -- we like to work with humans, which is really important to further build on the animal research. We're really doing our study to look at the underlying mechanism of why we think time-restricted feeding is important."
But why exactly is this fasting period so important, anyway?
"It's hypothesised that the extended fasting period then switches on certain genes that improve metabolism," Parr said.
"After every meal we've got a three-hour postprandial period where you're processing the energy and nutrients from that meal, and then it's another three hours until you're fasting.
"If fasting is only classified from six hours, then you would need to have more than six hours where you haven't consumed more food. But if you're snacking until midnight and then up at six or seven o'clock, then you're almost not fasting -- ever.
"If those fasting times are really important, which is what we think they are, then without having that fasting time, it may be why we're heading towards this obesity, type 2 diabetes epidemic."
At the same time as improving our metabolic processes, extending the fasting period (that is, reducing the time throughout the day eating) also means that we tend to 'miss' the time when we overeat junk foods. Yes, we're talking about that late night snack.
"Inherently, because people then avoided certain foods which are aligned with certain times of the day, it meant that their calorie intake was different," Parr said.
"Things like alcohol, soda, ice cream and chocolate -- things we consume at the end of the day -- were reduced by reducing the time window. It seems like quite a simple notion that might be more achievable than 5:2."
The study Parr is leading investigates just this, with the male cohort following a time-restricted feeding plan from 10am to 6pm for a five-day period.
"On the first day, they spend it with us at the lab eating within that time window. We also run an unrestricted comparative group where they eat between 7am and 10pm, which is pretty normal for most people," Parr explained.
"We're having a look at both the blood and muscle samples. We're really interested in what's happening in the muscle because it's the biggest use of glucose in our body, which regulates our blood sugars. If the muscle is healthier, then the body is healthier.
"That's all we're changing -- the time people eat."
Although the study is still ongoing, it potentially provides an exciting, achievable strategy to help people better manage their eating patterns and weight.
"We don't know how much of a magnitude of benefit there's going to be, but we do expect there's going to be a benefit from eating between that shorter time window," Parr said.
This certainly makes us regret poking fun at older people for eating dinner so early.
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