Over the last few years we got to see many studies and systematic reviews touting the benefits of intermittent fasting. A 2020 systematic review concluded that IF shows promise for treating obesity, which is a risk factor in cardiovascular disease, type 2 diabetes, cancer and non-alcoholic fatty liver disease (this one increases the risk of liver cancer). Considering that in 2018 approximately 63 percent of Canadians were either overweight or obese, there needs to be something that can help.
Can IF be the magic cure?
Some doctors swear by its effectiveness, and there are many (too many) voices in social media echoing its many positive effects: better metabolic health and lower risk of metabolic syndrome, lower blood pressure, increased autophagy* hence the possibility of slowing down aging and lowering the risk of cancer. Big claims, right? Too big to be true? It’s complicated.
*Autophagy is a process that happens in organisms that have a certain type of organelles (the equivalent of organs but in cells) called lysosomes, which act to digest bits and pieces that cells don’t need so they can be recycled and reused. It happens naturally without our input, by the way.
Of course it would be wonderful if we had a tool that could do all of the above and without too many or severe adverse health effects. BUT. And I’m not being dramatic, the capitals are needed. While there are positive health effects associated with IF done right, it’s not all pink balloons and happiness. A recent study of 20,000 adults over more than a decade showed some sobering results at a recent American Heart Association conference: an 8h eating window (and 16h of fasting), which is the timing people employ when they do the typical IF, increases the risk of dying of cardiovascular disease by 91 percent over the years. Clearly, you’re more than entitled to ask: what then? I agree, it’s unsettling.
Here’s some of what we know (or don’t)
- Most studies on intermittent fasting and fasting for longer periods of time, as well as calorie reduction were done on worms, mice and rats. Good for starters but unless we see the same results in humans, we simply cannot run with the conclusions and have everyone practice intermittent fasting (some people choose to eat one meal a day, others do one day on/one day off and some choose to fast for a few days which could be risky). Worms lived longer when they fasted, and mice and rats also had positive health effects plus in some other studies, they seemed to respond much better to cancer treatment. Sounds great, but… they are animal studies.
- We do have a circadian rhythm that we need to take into consideration and yes, most humans do better with getting their higher calorie meals earlier in the day (better insulin response in the morning). Most of us do well with the old ‘breakfast like a king, lunch like a prince and dinner like a pauper’. Eating when we feel like it and overeating, which often happens when we wait too long between meals, can lead to digestive issues such as bloating and discomfort, but it can also impact blood sugar and insulin levels.
- Calorie restriction (when needed to deal, say, with high-risk metabolic conditions and only under supervision) impacts weight loss. That’s non-debatable. As far as IF goes, a study published in Cell Metabolism showed that it can have positive effects on insulin resistance, blood pressure and oxidative stress, and it can decrease evening appetite. All that without affecting weight. However, an important detail: the study was done in men. Women respond differently to IF, even more so during menopause transition.
What to do with all this then?
The 16/8 window was not decided as a do-or-die part of the mice IF study (the grad student in the above study had a personal life too, hence the timing of feeding and fasting windows). In fact, research in humans showed that a 10h eating window (hence 14h fasting may be better health-wise and also more sustainable long-term). So why not do that. Eat an adequate amount of food during the 10 or 11 hours you decide works for you, and stick with fasting during the rest. Drink water, coffee or tea (no sweetener, even non-caloric ones) and be willing to adjust the timing or meal distribution if you’re struggling. It’s all about making it work long-term.
We’re not supposed to eat around the clock
I am not against snacking but it’s a modern-day thing, we have to admit. Taking breaks from eating at the end of each day allows our gut to do the maintenance work that ensures we are healthy (repairing the gut lining, getting rid of various metabolites or cell debris, etc). On the other hand, food is supposed to be enjoyed rather than feared.
The results of the recent study are unsettling to say the least. But let’s wait until it’s peer-reviewed and maybe there will be other similar studies to follow. It’s worth remembering that fasting is not a new invention. People have been fasting around the world for many reasons (mostly religious) and they lived to tell the story. Fasting can be a tool in our toolbox when needed more so if it can work to improve metabolic conditions. But we’re not there yet. We still need to find the right conditions to make it happen without adverse effects. Ideally.
