TRE, or time restricted eating, is fast becoming a diet buzzword for 2019. Here’s why some experts reckon that eating within a specific window has benefits for everything from weight loss to dental health

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Dr Michael Mosley  has been at the forefront of the success of the 5:2 diet , the Blood Sugar Diet  and the Clever Guts Diet , reversing his own type 2 diabetes  diagnosis in the process and getting both his blood sugar and body weight back into a healthy range. In his new book, The Fast 800 , he expands his intermittent fasting repertoire to make the process more “manageable”, with one particular focus being ‘time restricted eating’ (TRE).

What is time restricted eating?

TRE essentially involves eating all of your meals for the day within a designated time frame. In a recent article written for The Daily Mail , Dr Mosley stated that, for him, TRE involves “eating food within a strict 12-hour window. My plan is to finish eating by 8pm and then not eat anything until 8am the next morning.” His new Fast 800 plan also advocates this approach, whether you’re at the “rapid weight loss” stage or simply maintaining a healthy lifestyle (eating in accordance with the principles of the  Mediterranean diet  without calorie counting according to Dr Mosley). He explains that an overnight fasting period “gives your body a chance to switch its priorities away from digestion and on to other important functions, such as ‘autophagy’. This is the clearing away of old cells to make way for new ones. An extended overnight fast will also help your body switch from burning sugar to burning fat”

Dr Mosley isn’t the only medical expert purporting the advantages of time restricted eating of late, with GP Dr Rangan Chatterjee  declaring the idea to be a wellbeing gamechanger in his book The Stress Solution: The 4 Steps to Reset Your Body, Mind, Relationships and Purpose :

“I regard time-restricted eating to be one of the most important things anyone can do for their health.”

The benefits of TRE

While it’s by no means a new concept (diets such as the 16:8  involve eating all of your food within an eight hour time window, with a resultant 16 hour ‘fast’), time restricted eating is being promoted as an achievable way to practice intermittent fasting, with both Dr Chatterjee and Dr Mosley highlighting that twelve-hour eating windows can also pay off healthwise.

It complements our circadian rhythm

Dr Chatterjee attests that, like our body clock , our digestion also “runs on a daily rhythm” with our bodies “optimized to process food during daylight hours.” Modern life and shift work has thrown this up into the air for many of us, triggering higher insulin resistance and a greater predisposition towards diabetes in Rangan’s clinical experience, but this is where TRE can help according to Rangan. Early research in mice indicates that eating within an eleven hour window can aid weight maintenance and overall fitness, even if the mice ate a fast-food heavy diet. In Rangan’s view, “for most of us twelve hours sufficient to reap most benefits”, which is made easier when you consider that “you’ll hopefully be sleeping for about eight of the twelve hours without food.”

Dr Mosley also agrees with Dr Chatterjee’s ‘daylight eating’ preference:

“Studies show it is better to eat most of your calories early. That’s because your body is much better at handling sugar and fat in the morning than in the evening when it is getting ready to close down for the night and will not appreciate being forced to re-start the complex process of digestion.”

It can aid weight maintenance and loss

Not simply because it increases the body’s potential for fat burning according to Dr Mosley, but also because it gives you less time in which take in calories, in turn “imposing discipline and stopping you constantly thinking about your next meal.”

Obesity researcher and author of The Diet Fix  Dr Zoe Harcombe PhD subscribes to this view too but encourages tailoring TRE around your individual timetable without becoming obsessive - if you overrun your ‘window’ every now and again it won’t make much difference:

“I’m an early riser so overnight fasting has become a natural process for me. I tend to eat my breakfast, lunch and dinner early, but you should do whatever works for you. If you’re hungry at 5pm though, don’t wait it out for dinner just because it’s not ‘time’. Have a filling, nutritious dinner and then give your digestive system a rest. This is beneficial as as it means that you’re blood sugar isn’t on a rollercoaster overnight and it stops you from mindlessly snacking when you’re tired later in the day.”

TRE also has one slightly unexpected perk in this regard too…

It’s good for your teeth

Dr Harcombe highlights that TRE is also advantageous from a dental health  POV:

“Time restricted eating can be really beneficial for your oral health - you finish your dinner relatively early and clean your teeth, which can help to reduce acid erosion as you’re having a break from food and drink and it also gives dental health products more time to take effect.”

To make TRE as effective and easy to stick to as possible Dr Harcombe recommends eating three meals a day max, making them as nutritionally dense as possible to sustain you to the next meal or throughout your overnight fasting period. That said, she impresses the importance of not becoming too religious or stressed about adhering to specific eating windows all the time - often life is too complicated. Dr Michael Mosley also makes it clear that, while TRE can benefit everyone, the fast track phase of his new Fast 800 diet in particular isn’t suitable for those who are underweight, have an eating disorder or psychiatric disorder, have heart problems or high blood pressure. If you have a medical issue or condition he strongly advises checking with your GP before making any changes to your diet.

Which fasting diet plans do what?

Follow Dr Mosley on Twitter  @DrMichaelMosley , Dr Chatterjee  @DrChatterJeeUK  and Dr Harcombe  @zoeharcombe