Eat to Live: Time Restricted Eating
What if there was one simple lifestyle change that could increase your lifespan? Researchers who study the science of longevity and disease prevention have found that there is indeed one simple lifestyle pattern that can decrease the risk of cancer, heart disease, obesity, diabetes and more: don’t eat at night. It turns out that our bodies are designed to process food better during the day, and when we eat at night, we rob our cells and organs of much-needed rest and repair. Studies show that while of course it matters what we eat, it also matters when we eat.
The human body evolved to eat during the daylight hours, when it’s safe to collect and prepare our food, and not to eat in the evening, when it’s dark and dangerous to be outside. Fifteen percent of the human genome works on a body clock, and about 50% of those genes are involved in the metabolism of food. We know the brain has a circadian rhythm, but so do the pancreas, intestines, liver and more.
Now with the advent of electricity and demanding work hours, we typically have our largest meal of the day in the evening and often snack after that. Our meal patterns are not in alignment with how we evolved to eat and can be detrimental to our metabolism and our cellular repair mechanisms. Does it really make sense to consume most of our calories within hours of going to sleep? It’s like showing up to a restaurant at closing time: the cooking staff will not be happy. Eating at night has been shown to raise blood sugar and insulin, increase inflammation, throw off hormones and decrease the important daily cellular clean-out called autophagy. Under these conditions the body can become fertile soil for disease.
As a naturopathic physician I regularly monitor these blood parameters and show people ways to lower their risk factors with lifestyle changes and natural medicines. One of those ways is to just change when you eat. Eating breakfast, lunch and dinner within the daytime hours, before 7 p.m., and allowing at least a 13-hour fast overnight is enough to show benefits. Some experts recommend extending that fasting window further by having a later breakfast and an earlier dinner if you can.
Time restricted eating has even been shown to reduce cancer rates. In one study, of 2,500 breast cancer survivors who tracked their food intake for seven years, a strong association was found to when they were eating. Women who had at least a 13-hour overnight fast had a 40% decrease in breast cancer recurrence and an over 15% decrease in all causes of mortality, regardless of whether they were overweight or not.
Other conditions that have been shown to improve from extended overnight fasting are gastric reflux, fatty liver, cardiovascular disease and diabetes. Weight loss with this mechanism alone is modest, but it can add up over time. In a famous study, two groups of mice were fed the same number of calories, but one group was fed only during the mice’s daytime and the other could graze all day and night. The mice in the Time Restricted Feeding group lost more weight than the other mice. In similar human trials, weight loss is more significant because without even trying, people will consume about 200 fewer calories per day when they stop nighttime snacking.
Time Restricted Eating is a simple lifestyle change that anyone can implement. Your body is designed to thrive in those conditions. Pregnant women and people with blood sugar issues, eating disorders or other health conditions would be wise to consult with their naturopathic physician or family doctor before making any dietary changes.
A hot bath has benefits similar to exercise
Many cultures swear by the benefits of a hot bath. But only recently has science began to understand how passive heating (as opposed to getting hot and sweaty from exercise) improves health.
At Loughborough University we investigated the effect of a hot bath on blood sugar control (an important measure of metabolic fitness) and on energy expended (number of calories burned). We recruited 14 men to take part in the study. They were assigned to an hour-long soak in a hot bath (40˚C) or an hour of cycling. The activities were designed to cause a 1˚C rise in core body temperature over the course of one hour.
We measured how many calories the men burned in each session. We also measured their blood sugar for 24 hours after each trial.
Cycling resulted in more calories being burned compared with a hot bath, but bathing resulted in about as many calories being burned as a half-hour walk (around 140 calories). The overall blood sugar response to both conditions was similar, but peak blood sugar after eating was about 10% lower when participants took a hot bath compared with when they exercised.
We also showed changes to the inflammatory response similar to that following exercise. The anti-inflammatory response to exercise is important as it helps to protect us against infection and illness, but chronic inflammation is associated with a reduced ability to fight off diseases. This suggests that repeated passive heating may contribute to reducing chronic inflammation, which is often present with long-term diseases, such as type 2 diabetes.
Exciting new field of research
Passive heating for human health is a relatively new field of research, but some exciting results have emerged over the past few years.
Research from Finland, published in 2015, suggested that frequent saunas can reduce the risk of having a heart attack or stroke – at least in men. The idea that passive heating can improve cardiovascular function received further support when the University of Oregon published a study the following year showing that regular hot baths can lower blood pressure.
In a second study, the same group looked at the mechanism responsible for these improvements. They found that passive heating raised levels of nitric oxide, a molecule that dilates blood vessels and reduces blood pressure. This has implications for treating high blood pressure and improving peripheral circulation in people with type 2 diabetes. As type 2 diabetes is associated with reductions in nitric oxide availability, passive heating may help re-establish a healthier nitric oxide level and reduce blood pressure.
In order to establish the effect of increasing body temperature passively, as opposed to through exertion, another study matched the intensity of heating from water immersion to that of running on a treadmill. Water immersion resulted in a greater increase in body temperature compared with exercise, as well as a greater reduction in average arterial blood pressure. This is important as a reduction in blood pressure is closely associated with a reduced risk of developing heart disease. This study points to the promising effect that may result from passive heating. It also suggests some of the cardiovascular effects of passive heating may be comparable with those of exercise.
As well as the cardiovascular effects of passive heating, there is evidence to suggest that there may be beneficial metabolic effects as well – such as better control of blood sugar. The first study, conducted by Philip Hooper of McKee Medical Center, Colorado, in 1999, investigated the effect of three weeks of hot-tub therapy in patients diagnosed with type 2 diabetes. The results showed improvements in body weight, blood sugar control and a reduced dependence on insulin.
Hooper thought these effects may result from changes to blood flow as a result of passive heating, but he was unable to identify a specific mechanism by which their intervention led to these benefits.
Since this early investigation, few studies have investigated the potential for passive heating to improve blood sugar control in humans. With our study, we have tried to reignite interest in the health benefits that may be linked to passive heating.
Heat shock proteins
Heat shock proteins are molecules that are made by all cells of the human body in response to stresses. Their levels rise following exercise and passive heating. In the long term, raised levels of these proteins may help the function of insulin and improve blood sugar control. (Conversely, heat shock proteins have been shown to be lower in people with diabetes.)
It seems that activities that increase heat shock proteins may help to improve blood sugar control and offer an alternative to exercise. These activities – such as soaking in a hot tub or taking a sauna – may have health benefits for people who are unable to exercise regularly. Hopefully our future investigations, coupled with those of other groups worldwide, will help to establish the true potential of passive heating as a therapeutic tool.
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