Fasting has long been promoted as a cleansing tool, physically and spiritually, and is said to help one attain self-control and a deeper understanding of faith. But what’s the science behind it?
Fad or not?
Fasting is thought to boost metabolism and reduce the risk of chronic disease. In animal studies, fasting is shown to be associated with lower cholesterol, lower triglycerides and fasting glucose levels, less body fat, and overall better health—even a longer lifespan.
In one popular method of intermittent fasting, eating happens within eight hours (daytime) and the rest is fasting (unsweetened drinks only). During the time-conditioned abstinence with no available energy from food, the body uses the calories stored as fat.
The circadian rhythm connection
Insulin release follows the circadian rhythm, rising by day and dropping at night, which explains why we seem to deal better with richer meals earlier in the day. The belief is that our circadian clocks are designed to help us stay healthy as we go between feeding and fasting.
With the arrival of artificial lighting, the boundary between day and night became blurred, and not without consequences. Shiftwork, social engagements, or bad habits have us eating calorie-rich meals and snacks late at night. Obesity and diabetes (due to insulin resistance and high blood glucose levels) are on the rise. So are cancer and heart disease.
Perpetual snacking can make us overwrite hunger signals, and we grab another handful. That keeps the body in a perpetual “fed state,” while fasting helps the body switch to breaking down stored resources and performing repairs.
Did you know?
A large cohort study concluded that late eaters (those who often ate after 9:30 pm) had an increased risk of cancer.
No less important are the recent revelations on the microbiome. Our inner team of bugs, normally in sync with the circadian clock, are now believed to adapt to our late-night shenanigans at a price, by making it even harder to resist after-hours temptations. Moreover, the required night-sweeping for cellular regeneration purposes is affected too.
Exercise to the rescue? Before you go for that late-night treat with promises of running it off tomorrow, consider this: exercise alone is not thought to prevent food timing-related diet-induced obesity. Instead, aim to avoid nighttime eating when possible so you work in sync with your circadian clock.
Effects of fasting
Animal studies showed that intermittent feeding prevents excessive body weight gain and halts the effects of obesity and metabolic diseases such as type 2 diabetes, by decreasing insulin resistance and improving glucose tolerance.
“There are studies showing that intermittent fasting decreases inflammation and reduces oxidation, and it reduces the risk of heart disease,” says Orsha Magyar, MSc, registered holistic nutritionist in Calgary and founder of NeuroTrition.
Contrary to what we might expect, whether associated with weight loss or not, intermittent fasting increased physical fitness performance levels in a rodent study.
Increased lifespan? Multiple studies on many organisms, from yeast and worms to mammals, concluded that fasting promoted longer, healthier lives. Fasting has been shown to help rodent brains too. “Intermittent fasting increases the brain production of a special kind of protein, which helps neurons grow and stay healthy, and it may even protect against neurodegenerative diseases,” says Magyar.
Asthma-related symptoms were also improved with fasting in one 2007 study of overweight men.
Fasting mice developed fewer and slower-growing tumours in one study. Plus, preliminary research on cancer patients is showing that short-term fasting may help protect normal cells from the adverse effects of chemotherapy drugs, but not cancer cells, making treatment more effective.
Pre-diabetic men who underwent intermittent fasting had lower blood pressure, reduced inflammation, and lower insulin—regardless of weight loss.
Fasting is not for everyone
“Some people may experience improved health outcomes on intermittent fasting; for others it may not lead to any changes or may cause negative health outcomes,” say Alexandra Inman and Stephanie Dang, registered dietitians at Vancouver Dietitians. No single diet plan works well for everyone, they add.
Children and teenagers should not fast, as their developing bodies need a constant supply of nutrients.
“We recommend that people with chronic diseases such as diabetes, cardiovascular disease, or cancer, do not fast, as they’re at risk of becoming malnourished,” say Inman and Dang. Also, they add, don’t fast if you’re pregnant or planning to become pregnant, or are breastfeeding.
Don’t fast if you have diabetes or take blood pressure or heart medication, as it can affect the electrolyte balance.
“Intermittent fasting is a beneficial way of eating, but not for everyone,” explains Magyar. Don’t fast if you have any blood sugar issues, she cautions, as you’ll risk hypoglycemia.
Make sure you speak to your health care practitioner before adopting the diet.
Fasting or not, eat healthy
Fasting cannot counteract the negative health effects of a diet high in fats and refined carbohydrates. In other words, skip the snack aisle and shop the perimeter of the store where the wholesome foods are.
Fasting can prove helpful in preventing or even possibly reversing metabolic disease symptoms and reducing cancer risk, but it is by no means the silver bullet. “Focus on incorporating more vegetables, fruit, whole grains, and plant-based proteins such as legumes, tofu, and nuts/seeds and their butters into your diet to make sure you’re getting the nutrition you need,” say Inman and Dang.
Monitor the impact on your lifestyle, whichever fasting method you choose:
- 5:2 method—eat normally for five days a week, then switch to 600 calories for the remaining two
- alternate-day method—alternate between regular feeding days and fasting days with just 500 calories or so daily
- 16:8 method—eat for a period of eight hours and fast for the rest with water and unsweetened drinks
“You need between three and six weeks to adapt to intermittent fasting,” advises registered holistic nutritionist Orsha Magyar, so be patient but aware of how you feel.
Cook for the love and health of it, and make meals a social affair. “The reasons that people eat are for more than just nutrition. Our food choices are impacted by social, economic, environmental, and cultural factors,” say Inman and Dang.
Food is not just nutrition: enjoy every bite, but choose healthy options whenever possible and remember your circadian clock.
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