Time restricted eating: when you eat matters

Intermittent fasting is an increasingly popular phenomenon among people wishing to improve their body composition and their overall health – almost as much as consuming the latest superfood.

Intermittent fasting (or time restricted eating, as it is known in the scientific literature) is when we restrict our eating during the day to a window of from around 8 hours to 12 hours, and has been popularised by the fitness industry in recent years. There are different ways to approach it, though from a health perspective, eating earlier in the day to allow for the feeding to align with our body’s circadian rhythm may optimise the health benefits for overall longevity. Fasting has been a practice undertaken for centuries in some cultures, and research reports favourable effects on many markers of metabolic health, including blood lipid profile, blood glucose metabolism and hypertension when these populations have been studied. More recently, researchers have investigated different time restricted feeding protocols in relation to risk of cardiovascular disease, neurological disorders, diabetes and some cancers using rodent and human trials. The longer time spent fasting may have pronounced health benefits, though recently a more conservative method (of even an 11 hour fast) has emerged as being beneficial for certain populations. Indeed, time restricted eating is being thought of as an easy to implement, effective lifestyle intervention that could help improve appetite control, markers of overweight, inflammation, blood glucose metabolism and hypertension, all reducing risk of cardiovascular disease, diabetes and some cancers. This recent small study found that late night (or prolonged eating periods) increased fasting glucose, blood triglycerides, insulin and weight gain.

When healthy adults eat meals that are identical in terms of macronutrients (ie carbohydrates, proteins and fats) and caloric load at breakfast, lunch and dinner, the postprandial (ie. after eating) glucose response to the meal is lowest after breakfast and highest after dinner, even though the meal is identical. This is one example which suggests that our metabolism, and response to food, changes across the course of the day (see here). We are diurnal creatures – we do most of our activities during the day (including eating, working, exercising) and we rest at night. This is controlled by our internal clock in the brain, the superchiasmatic nucleus (or SCN) which in turn influences smaller internal clocks (or oscillators) in the peripheral tissues of our body. These clocks control thousands of genes within our body, including those that regulate our metabolic processes, which accounts for around 10% of our entire genome. While light is the major cue for the SCN in our brain, timing of food intake influences the circadian rhythm in the other tissues, including the liver, which has implications for metabolism. This tells us that our basic metabolic physiology is supposed to behave differently according to the time of day – this is everything from making neurotransmitters, to making insulin, to glucose transport inside of cells, to fatty acid oxidation and repairing cellular damage. It makes sense then that when we eat has just as important implications for our health as what we eat. Research investigating the health effects of fasting has found that anything that breaks the fast will break the fasting period, including no calorie options such as black coffee and even herbal teas. This is because there are compounds within these fluids that require breaking down by the liver. That is not to say that people don’t experience benefits from fasting if they consume a hot beverage earlier in the day (as is often recommended to help get through the morning hours and comply with a 16:8 protocol) or limited calories (for example, 50 calories), however longevity benefits may well lie within the strictest definition of fasting.

With the advent of artificial light, and the changing structure of work schedules (combined with the increasing busy-ness of everyday life), this has elongated the period of time that people eat, which has negative health consequences. While you may have heard in media reports of scientific studies that eating late at night makes no difference to overall weight loss, the focus on weight ignores the more important, underlying metabolic and chronic disease risk that eating late into the evening can have on health outcomes. It may be easier to regulate appetite too, as  research suggests that appetite hormones respond more favourably to eating earlier (8am to 7pm) than later (noon – 11pm), and the level of satiety achieved with this could prevent overeating. This is relevant with time restricted feeding as research has shown that more frequent eating patterns can be detrimental to metabolic health if consumed close together. One study found that participants who ate excess calories consuming their food over three meals and three snacks had increased visceral (stomach) fat deposition, liver triglycerides and lower liver insulin sensitivity compared to those consuming the same number of calories over three meals. The snacks were consumed later in the day, and after each meal, so elongated the overall eating period.

Animals limited to 9-12 hours feeding period, but not limited in the number of calories they eat have experienced benefits including decreased fat mass, increased lean muscle mass, improved glucose tolerance and blood lipid profile, reduced inflammation, higher volume of mitochondria (the energy powerhouse of our body), protection from fatty liver and obesity, and a more favourable gene expression. In humans, research studies suggest that eating within a time restricted window of 11 hours (say, 7am to 6pm) is associated with a reduction in breast cancer risk and occurrence by as much as 36%. Earlier eating time has resulted in more effective weight loss in overfat people, and every 3 hour increase in fasting duration was linked with 20% reduced odds of having an elevated glycated haemoglobin (HbA1c), a marker of long term blood sugar control. For every 10% increase in calories consumed after 5pm there was a 3% increase in c-reactive protein, a biomarker used to measure inflammation (the underlying process that, when elevated long term, can influence risk of diabetes, cardiovascular disease and some cancers). Finally, when meal times were constructed earlier in the day this resulted in a 10% decrease in c-reactive protein. Eating within a 12-hour window improved sleep and weight loss within an otherwise healthy population. You can see then, the myriad of potential benefits to eating within a time restricted eating – could it be worth trying to fit into your lifestyle? And if so, how to do it?

There are many different time restricted eating protocols to choose from – and the type of fast you choose to do really comes down to what works for you. The 16:8 protocol that seems to be most popular is a little aggressive for anyone new to fasting, and this may ultimately leave you feeling hungry, cranky, and vulnerable to overeating later in the day – undoing any potential health benefit that has been shown in the research. Indeed, many people I see that try this as their first experience report that they can successfully get to 11am or lunchtime without eating, but once they are home from work, no amount of food will keep them full, eating right up until bedtime.  My advice is to start a little more conservatively. Given that (in an ideal world), we sleep for 8 hours a night, not eating in the 3 hours leading up to bed time should be a good place to start for most people, thus it gives that 11 hours where some of the health benefits begin to be realised. From there, once adapted, you could try to push it out by an hour. While the most potent benefits occur with the strictest definition of fasting, the blood glucose and lipid improvements, along with fat loss can still occur in those whose definition of fasting refers to calories, not coffee and tea as mentioned above. That the benefits occur in the absence of caloric restriction is important to reiterate, however by restricting the eating period, many people also reduce overall caloric intake, which can further improve overall metabolic health and body composition. Fasting doesn’t appear to be something you must do every day to see the health benefits either, and even 3-4 days a week could be beneficial for metabolic health.

That said, this reduction in calories and extended time NOT eating may not be good for all, especially if your notice increased anxiety, sleeplessness or disruptions in hormone balance, so it is always best to proceed with caution. It would also be prudent for any individual with a health condition to discuss with their health professional before embarking on time restricted eating, especially the more aggressive protocols.

(PS I’ve got dates booked for Nelson, Wellington, Dunedin and Christchurch for my talk! Click here to find out more details, would love to see you 🙂 ).

clock

As with many things, it could be all about timing…

Another mindset shift: (lack of) training for the marathon.

Another marathon ticked off. And this is the first one that I’ve completed as an LCHF athlete. More than that though, it’s the first one I’ve raced on a smaller training load than I thought I needed. And while I say ‘oh, I don’t race’ – in reality, when I step up to the start line and the gun goes off, I am racing. It’s a race against the clock and myself, and not the people around me, though I did earmark one dude on the start line as my nemesis that I wanted to take down – and this had nothing to do with his running ability.  This was purely because he was in a tutu and as soon as I saw him I thought ‘there’s no way I’m letting anyone in a skirt, guy or girl, beat me.’ Rational? Obviously not.

I entered the Queenstown marathon at the start of the year purely because the early bird deal was so good. As a new event, they took $50 off the entry fee for the marathon and, like anyone who likes a bargain*, that was enough for me to sign on the dotted line. Inevitably, though, life and limb gets in the way of any decent build up period for a race and more often than not I’m left with 8-10 weeks to go and starting to panic that I’m not going to have the time for an adequate preparation period. Now any coach would look at that length of time and say that it was ridiculous to think it wasn’t enough time. Physically, of course it is – particularly as it’s not like I’m going from a couch potato to my first marathon; I’ve been running for over 20 years. Psychologically though: different story. Particularly when your compatriots are 6 -8 weeks into their 16 week build plan for an event and ticking off 8-10 km intervals on a Saturday, backed up with a 2h 15min run on a Sunday and I’m high fiving people for completing a 40 min easy run without any nagging sensation in the calf. I’m obviously excited to be running, but daunted by what is ahead in terms of ‘making up’ lost kilometres to get me on an even par with other runners of my ability. It’s easy to talk yourself out of a good race before you’ve even begun to train for it. I know I do. And, even when you do train for it, how many people do you know line up on the start-line with either a niggle, a virus, or lack of preparation to blame their less than ideal finish time on?  Not only do I battle with knowing that others have been able to consistently run at a time where I’ve only been able to do gym work and some swim sessions, but my main problem is that I have a fear of failure. This has been the hardest thing to let go of over the last few years – the expectations that I perceive others have of me and my running ability.  In some ways not having the ideal race build up let me off the hook; it’s a legitimate reason for running slower than others think I’m capable of – and just finishing the race is good enough. Bevan, though, didn’t let me off that easy. He guided my training for the Queenstown marathon and was adamant that 8 weeks was adequate to get me in pretty good shape to get around.

Previously, I would have tried to cram in as much running with intensity as I could tolerate, with a couple of rest days per week, so I would build my fitness faster that way. Bevan had a different approach. He pointed out that whenever I get injured in the past, it is from the combination of both longer runs plus interval training which places too much stress on my body. Hmm… good point. He predicted that, if I were to include intensity along with duration in my build up, I would break down at roughly 4-6 weeks in, leaving me in a spectator role come race day, as it has in the past. Needless to say, that put the kibosh on my grandiose plans of the interval/long run double that is the mainstay of any running programme. Instead, he suggested that I needed to focus on frequency. Just run. Everyday. The length of the runs varied from 25 minutes to 2h, and while I would lift the pace on some runs, there were no set tempo sessions, hill repeats or one kilometre intervals. It was just running. Part of me loved it – telling a runner that they can run everyday is like letting a sugar addict loose in a candy store. In addition to that, while I LOVE running, I actually really don’t like running those 2 1/2 – 3h runs which are another mainstay of a running programme. They to me are almost the necessary evil of marathon build-ups that sap your reserves, leave you feeling broken and ancient for the rest of the day, but at the same time almost perversely thrilled that you’ve ticked off the big miles that distinguish you from that half marathoner runner.**   A big part of me though was anxious that this preparation would leave me short on race day. How was I supposed to get around 42.2km when I hadn’t run for longer than 2h on any long run?

But I listened dutifully to what Bevan told me, switching it up a bit with my pace – some days it was closer to 6 min kilometer pace, something I would never have considered doing in the past but had become almost worryingly easy to do now. Others we would run a steady 20 minutes at around 4.40 kilometer pace as part of our long run. But, bar one run that was around 2.04 and in hideous weather at a hideously slow pace, I never went beyond those guidelines. I got up every morning and ran, once a week was 2h, once a week was 80 min and the rest were between 25-60 minutes – and, as Bevan said, I made it to the start line in one piece. And while I still wasn’t convinced that I had run long enough in any long run to get through the event and feel okay, you know what? I did. Other than that inevitable dip that occurs in ‘no mans land’ from around 27-32 kilometers, I felt comfortable, strong, I paced it pretty well (the second half was four minutes quicker than the first) and came in at 3.28 and some change. It’s not my fastest – actually it’s slower than my PB by 37 minutes, but I felt awesome. That I made it to the start line and finished in one piece on such a spectacular course are three wins in my book. As a runner, I love to be able to run and I think this approach will allow me to do that. This has provided me with the ‘proof’ I need that I don’t need to do the extra long training runs to successfully complete (and run pretty well) in an event. This is a massive shift from days of old, and the runner mentality. My goal in running these days isn’t to aim for another PB; I don’t have the mental energy required to do that, nor do I want to. I just want to be able to run, enjoy it, participate, push myself and enjoy the afterglow of a run well run. Who knew that you didn’t need to run hard and long to do that? This might not be a major for another runner – but for me it is almost as much of a mind shift as the LCHF approach to marathon training. Stoked to have made it.

PS The guy in the tutu totally took me out – so did another very talented woman runner in a Lululemon running skirt. At the risk of making myself wildly unpopular, I am not a fan of the ruffled skirt number.

*aka any runner because as a group we are known for being frugal – though anyone who runs will testify that it ISN’T a cheap sport

** no disrespect intended. I love half marathoner runners. In fact some of my best friends are half marathoners.