Circadian Diet

Bronwyn's picture

Dear Thomas Edison,

What were you thinking?


The Public Good

As we all know, the electric light bulb changed everything about how our social and industrial world functions. Without the pesky constraints of things like night time and winter, we can work, play and eat around the clock. Awesome, right? As it happens, there’s a downside. We’ve all heard about how light affects sleep, but there are also some fascinating studies showing the deleterious effects of spending large portions of the 24 hour clock in a feeding rather than fasting state. Who knew that something as ubiquitous as the electric light bulb could play a role in so much diabetes and heart disease?

On my patient’s first visit, I gather a lot of information about diet and lifestyle.This usually includes outlining an average day: when do you wake, when/what do you eat, when’s bedtime. In my observation, the average working person in a day job will wake at 6, breakfast at 6:30, work all day, dinner at 7pm, maybe a snack later, then bed at 11. In this scenario, you’re actually in a “feeding” state for over 12 of the 24 hours. So why is this a bad thing?

Increasingly more study is being conducted on the health and lifespan effects of different types of fasting. There are metabolic states associated with fasting that cannot be replicated during feast time. The fasting period serves as a time for standby and repair so that the organism is fit and competent to harvest energy when resources, such as food, become available. From an evolutionary perspective, this discreet window of food availability makes perfect sense. We need to be capable of storing and using energy for periods of scarcity, without losing fitness or vitality. In fact, there are studies where bacteria are kept in a nutrient rich suspension, and when the nutrients are removed, so they are left in simple water, their lifespans double. It’s true that we are not bacteria, but similar results are seen with increasing periods of fasting in rodent and human studies.

The idea of fasting can be very daunting. In fact most people would just as soon be unhealthy as have to skip a day of eating. Fair enough; when you fast for the first time, it can be profoundly uncomfortable. However, there is more than one way to “fast”.

In “Intermittent fasting”, you consume ~500 calories for one day, followed by 2-3 days of normal eating. This constitutes one cycle, which would then be repeated.

“Periodic fasting” refers to fasting for periods of 2 days in a row, with a one week break between cycles. Both of these options are difficult to implement, as, given our lifestyles/work obligations, compliance is low.

However, there is a form of fasting called “time resticted eating” which is a much more managable regime. In this model, patients follow a cyclical eating pattern based on a daily circadian rhythm. So, for example, you can wake at 6, have your breakfast at 10, dinner at 6:30, and consume only non-caloric beverages until bedtime at 10. With this regime, you can garner all the beneficial metabolic effects of fasting, such as reduced insulin resistance and increased glucose tolerance. The upside is that you can still consume the same number of calories, as long as you do it within that window. Subjects who followed this regime in studies show a reduction in body fat, primarily visceral or “brown” fat, irrespective of caloric intake.

So if you’ve “tried everything”, give time restricted eating a chance. If you have any questions about your specific health concerns, book a 15 minute phone consultation today.