Should I do intermittent fasting for weight loss?

Ok, catch me up: It seems like every health outlet is talking about the latest weight-loss craze, intermittent fasting (IF). Truth is, this “dieting” technique isn’t new but rather it’s making a comeback. 

 

I’ve heard of it. What do I need to know?

IF is simply not eating for a majority of a 24 hour day. So for example, you choose an 8-hour time block of your day that you will eat all your day’s food and nothing in the remaining 16 hours of the day. It’s not about what you are eating or how much, but rather solely about when. This technique is supposed to lead to weight loss because in the hours we are not eating our body will feed on its stored energy. IF has you follow this guideline for most of the days of the week and then a more typical meal schedule for the others. 

 

What tends to happen with IF, is that not only is withholding from eating difficult for people, making this lifestyle unsustainable, but your weight loss plateaus as your body adjust to this new eating schedule. 

IF explains that our body will use its stored energy (glycogen from our liver and body fat) that was not metabolized for energy when we ate (feeding state) and will become our energy source in a fasted state. 

 

Doesn’t sound realistic. What can I do?

IF is an oversimplified version of Timed Nutrition (TN). The idea of taking a break from a feeding state isn’t wrong. Our metabolisms are strongest in the earlier part of the day, in this way the idea that when we eat matters is true. However, it’s not about only eating for 8 hours of the day, it’s about eating when our body wants us to be. TN is about having your first meal of the day about 2 hours after waking up, your last meal about 3 hours before going to bed, and eating most of your calories at your morning and afternoon meals with a smaller last meal. TN creates a sustainable lifestyle rather than about creating a fasting state for your body to feed off its stores. TN  strengthens your metabolism by using our body clocks (circadian rhythm) to set our mealtimes. 

If you are trying to lose weight, we know that it matters WHAT we eat. But you may not realize that it also matters WHEN we eat. 

 

Our bodies have central clocks in the middle of our brain, right where our optic nerves cross, allowing the clock to respond to night and day. Recently it’s been discovered that there are also clocks in every organ of our body (heart, lungs, kidneys, etc.) known as peripheral clocks. Importantly, our entire digestive tract also has a clock. The rate at which our stomach empties, secretes digestive enzymes, and expresses transporters and processors for glucose and lipids in the intestine, all cycle around this clock. Our health may depend on keeping all these clocks in sync.

 

Our circadian rhythm is meant to get a bright light push every morning at dawn but if the sun rises at a different time or we are exposed to bright light in the middle of the night (like when we travel across time zones) this can push our cycle out of sync and leave us feeling out of sorts. This is an example of a mismatch between the environment and our central clock. Evidence shows that chrono disruption, the state in which our central and peripheral clocks diverge out of sync, can play a role in conditions ranging from premature aging, cancer, mood disorders, and obesity.

 

Bright light exposures are the synchronizing swing push for our central clock, so what drives our peripheral internal clocks that are not exposed to daylight? Eating food! That’s why the timing of our meals may be so important. You can decouple central from peripheral rhythms just by shifting meals times. Leading to metabolic disarray. For example, the same way morning light can help sync your central clock in your brain, morning meals can help sync your peripheral clocks throughout the rest of your body. Morning meal skipping disrupts the normal rhythm of these clocks that coincides with the adverse metabolic effects. 

 

This means that we can control our peripheral clock and its sync with the central clock rhythm by timing our meals appropriately. Eating your first meal about 2 hours after waking up, then an afternoon meal and an afternoon snack, and ending with an evening meal time for 2-3 hours before going to sleep, can balance your digestive tract body clock with the rhythm of your central clock. 

 

Great! Where do I start?

Eat within an 8-12 hour feeding window in the earlier part of the day. Stop eating after dinner, about 3 hours before bed, and only have water and tea after.