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 🙂 ).


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

Nigel’s diet… why so much meat?

Thanks to Nigel there was an explosion of interest in my blog post last week – and with it, a lot of questions around including certain foods in my recommendations. One I’d specifically like to address is the inclusion of animal protein (or red meat) in (what some viewed as) large amounts. Now for those who have been reading my blog for a while, this will be covering old ground as I know I’ve talked about elements of this previously. However Nigel’s documentary series has sparked much more interest in what to eat and, as the questions I got suggest, a lot of this information is new ground for many – so I’m happy to delve further into some of these issues and explain why I encourage the inclusion of red meat in the diet.

The first point to make here is that a whole-food/paleo diet (as I recommended Nigel eat) is not a meat heavy diet – it’s good to dispel that myth immediately. Sure, some doing ‘paleo’, include large amounts of meat at every meal at the expense of vegetables; however that is not what most people I know do. In fact, I eat more vegetables than some vegetarians I know. The inclusion of small amounts of meat or animal protein at each meal helps stabilise blood sugars and prevents overeating due to energy crashes. In addition, these foods contain complete proteins that are essential for the repair and rebuild of musculoskeletal tissue, they provide (amongst others) iron, zinc, iodine (fish) which are important for over 200 metabolic processes in the body important in brain, gut, liver and thyroid health, and deliver important antioxidants such as co-enzyme q 10 for heart health (and great skin!) Alongside these are the fat soluble vitamins (A, D, K) and essential fats (omega 3 fatty acids, monounsaturated fats and saturated fats) and cholesterol that form the backbone of many hormones and messenger enzymes that are responsible for delivering instructions throughout the body.

I’ve taken a broad-brush approach to the many benefits of including animal protein in the diet, but one thing I want to point out is that it’s not the eye fillet steak and the boneless, skinless, (tasteless) chicken breast that I’m talking about – the meat that is closest to the bone is the most healthy meat. Yes it’s fattier – but that’s a good thing (see above re: essential fats). There is beginning to be a trend of nose-to-tail eating now, making many of the offcuts of meat that were often binned now available to be purchased and used at the fraction of the price of an eye fillet steak (if people are willing to try them!). In New Zealand we have predominantly grass fed meat, which means we are largely protected from meat that has been grain fed. Grain fed cattle produces meat with a higher fat content but its fatty acid profile is not ideal – higher in omega 6 fats and higher intramuscular triglycerides (pro-inflammatory). The grain affects the health of the cattle, with more risk of infection and harmful bacteria which have downstream consequences to the quality of the meat we find in our food supply. While in NZ cattle are ‘finished off’ with grain, after a Twitter conversation I had the other week I believe the health consequences of this for us are negligible – though am happy to stand corrected!

And then there’s the issue of meat and cancer. And meat and heart disease. And meat and [insert health condition here that suggests you are a medium-rare steak away from certain death]. The problem with the media snippets most people are exposed to is that the finer (read: important) details are overlooked in amongst the rush to print that meat is as bad for you as smoking. Well (gasp) it’s not. Firstly, any research that suggests meat is adversely linked to any of the aforementioned conditions is association, not causational. These research studies cannot determine cause and effect and are not designed to do so. Secondly, many of the large trials asked participants to report their retrospective meat intake over a 6-10 year period once, in a questionnaire format (many people I know struggle to tell me what they ate last week). Thirdly, the distinction between actual meat and that which is found in a hamburger (for example) or even a meat sandwich in some cases is not made. There is a vast difference in quality between a rump steak and a sizzler (not to mention the latter is only around 45 percent meat and isn’t legally allowed to be called a sausage). People seldom eat a hamburger without a bun (this was before the advent of an ‘oxygen’ burger from Burger Fuel) and lumping a person who eats burgers five times per week (and upsizing with the fries and Coke) in the same category as someone who dines on eye fillet at a Pete Evan’s paleo restaurant five nights a week is problematic. Of course, I’m speculating here as to the overall diet quality of participants – but that’s all I can do as these important details pertaining to other nutrients known to affect health (i.e. processed refined carbohydrates, industrial seed oils) aren’t known. Many other lifestyle factors that contribute to poor health (such as a low level of physical activity, smoking, higher alcohol intake) are also seen in those with the highest intake of red meat and in some instances there wasn’t a linear relationship between meat intake and health (or death….) with the death rate falling in between those with the lowest intake and those with the highest intake (when split into groups according to overall consumption patterns.) These details mean little however when it comes to health reporting in the media. Nothing sells like sensationalism, and if we can draw parallels between red meat consumption and smoking then you don’t even need consumers to read the article to guarantee you’d have made an impact. Again, this is my Women’s Weekly overview; for a far more eloquent and in-depth critique of this, go to Zoe Harcombe’s review or Jamie Scott’s blog post discussing this issue.

Another big pushback against the inclusion of meat is from an ethical and sustainability perspective. Now I’m not at all suggesting that people who choose not to consume animal products based on their moral standpoint should reconsider. This is a judgement call I have no business in commenting on. However for others, thankfully the availability of free range meat now accessible at relatively cheaper cost is increasing. Demand also affects supply, and the more we ask for free range meat and eggs, the more the price will be driven down (especially considering its not essential to be choosing eye fillet for every meal). Another argument against encouraging meat consumption is that it’s not sustainable for the environment, with more demand for meat increasing the fossil fuel used to produce it, the water usage required and an increase in the methane emissions (and the carbon footprint). If we put it into perspective, most of what we do has a carbon footprint. Grain-feeding cattle may (or may not) be more resource intensive (and have a larger footprint) given what is necessary to grow the grains to be fed to the cattle as opposed to raising cows on a grass field. And promoting a vegetarian diet based on this argument is flawed given the resources required to feed the world on vegetables.


Turn your heating off a put on a jersey instead.

So that’s my stance on including animal protein (and red meat) in the diet. There are many reasons why people choose not to include red meat in their diet – but if they are based on optimising nutrient intake, protection from later chronic illness, or from a sustainability perspective, then perhaps reconsidering it wouldn’t go amiss.


Cancer: you suck. (A random collection of thoughts based on recent events).

Cancer. The scariest thing about it to me is just how random it seems to be. Yes, there is definitely a genetic component – for some types of cancers more than others – but equally sometimes it just hits. Out of all of my family, we would likely all agree that I’m the one that has lived as close to the ‘healthy’ lifestyle out of everyone. There was once a time where five of the seven of us smoked. Dad and I excluded (I took it up when I was 11y old, then had to quit a week later as Kylie Wirepa, the friend that had also decided to start smoking with me, said she had a heart murmur. Thank god!) While my family have begun to be more interested in their diet over the last 10 years or so (for various health/weight reasons) and intermittently jump on the exercise bandwagon, consistently only Dad and I would be the ones that – all things equal – would be the least likely to be diagnosed. All things being equal. But that’s not how it works. A close friend of mine has just found out that her sister has aggressive breast cancer that has spread to her lymph nodes. She described her as the ‘healthiest’ out of all of them* – the ‘alternative’ soy-drinking, non-smoking, moderate drinking, exercising sister when compared to the rest of her family.

Cancer is the uncontrolled growth of abnormal cells in the body. Instead of growing old, dying, and being replaced by new cells, cancer cells are cells that become damaged replicate, and then the mutation is replicated yet the cell doesn’t die – they continue to accumulate and form a tumour. When we studied the pathophysiology of disease in nutrition I remember Murray Skeaff teaching us that those predisposed to cancer can stay cancer free their entire life – there can be a long a latent period, if you like. However if they are exposed to risk factors, then this can start the process of cancer developing. Lifestyle can play a large part in determining risk of developing chronic conditions, as you know. Looking at the epidemiological evidence, a high intake of fruit and vegetables, maintaining a healthy weight, regularly exercising, a low alcohol intake, oral contraceptive pill use and hormone replacement therapy are all linked to an individual’s risk of breast cancer. This doesn’t determine cause and effect, but gives an idea of the types of lifestyle factors associated with the risk of developing it.

We discussed the fact that her sister avoided dairy and drank soy milk in the interests of health. Interestingly, there is a lot of controversy around the consumption of soy and breast cancer risk. Soy and soy products contain isoflavones a particular class of phytoestrogen that interacts with endogenous estrogen signaling pathways. Isoflavones can either block our endogenous oestrogen from being taken up in the body, or can increase the oestrogen receptor activity. This impacts our risk as increased exposure to oestrogen can drive hormone-related cancer. Asian populations have long consumed soy in its unprocessed or fermented form, in foods such as tofu or tempeh, whereas Westerners more commonly eat it either as dietary supplement or as a source of an industrial seed oil and protein substitutes. Nowadays, proteins or oil of soy origin also appear in numerous food products – such as infant soy-based formula, bakery items, (biscuits, doughnuts and cakes), fast foods (hamburgers, chicken nuggets, takeaway hot chips and pizza dough), cereal bars, protein bars and salad dressings. However the isoflavone content of these processed foods is far less than the traditional Asian diet – the typical Western diet consuming less than 1g/day, compared to intakes of up to 30g/day in Korea or Japan.

For women who are of Asian ethnicity, who have consumed whole soy products (such as soy beans) and fermented soy products (Natto and tempeh two such examples) their entire lives, in small doses, have a reduced risk of developing risk cancer. The relationship with European women is not the same. It is thought the processed nature of soy products, that they aren’t in their whole form, and they are consumed in the context of the Westernised lifestyle, changes the relationship. Indeed Asian migrant women have a higher risk of developing breast cancer when moving from Asia to the US. Women in Asian eat less processed food and have less of a caloric dietary load overall – these two factors undoubtedly contribute. Statisticians can adjust away a lot of factors to find significant relationships within epidemiological evidence – but many argue that, in real life, you can’t account for the differences in lifestyles that contribute to higher or lower risk regardless of the p value.

As we sat around on Friday night it’s fair to say that the rest of us were reeling a bit from the news too. Obviously it’s not the first time any of us have had someone close to them be diagnosed with cancer, but its sobering that, where once it seemed to affect those in the older age group more than anyone else, increasing numbers of younger, fitter, healthier people are being diagnosed with cancer – of all types. Yes, mortality rates are decreasing – increased awareness, earlier diagnosis and better treatment will all contribute to this. But more and more people are living with chronic illness and reduced quality of life – affecting them and those around them. Anyway, in my normal Women’s Weekly approach to this blog, this isn’t to educate you on the metabolic pathways and how these interact with diet and lifestyle to impact on your risk of cancer. Indeed I didn’t even mention sugar – I could write a book on that (likely don’t need to, I’m sure it’s been written). It’s more a reflection based on recent events. That’s fairly obvious actually, if you just look at the title of this. I couldn’t put a title on this that gave you an idea of the content – this is just a collection of thoughts based on recent events.  One thing that my friend did say was that her sister is someone who tends to stress more than most people. This has a massive bearing on our overall health and wellbeing and may, down the line, be found to be THE most important contributor to ill health. Diet, lifestyle, physical activity and sleep patterns all contribute to this. As we start to reflect more on how we live our lives and the concessions we make to keep up with what modern life demands of us, I think more people may look to take a step back and try to do things differently.


*– though she is no slouch when it comes to the health front, especially over the last couple of years as she’s switched from a higher sugar diet that included processed food to a paleo-approach to diet.