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Prolonged fasting

Not for the faint of heart.

Intermittent fasting

Learn about the benefits and the risks.

Time-restricted feeding

The best balance of both worlds.

Fasting in all its glory

Full out fasting

We all know that caloric restriction leads to weight loss.  Living with a small calorie deficit, but nutrient dense diet seems to increase health, but what about no calories at all?  Fasting, or not eating at all, is a surefire way to lose weight, but is it irresponsible?  Is it safe?  If the permanent solution is long term lifestyle change, then is fasting even worth it?

The longest recorded fast, while being supplemented with vitamins and minerals, is listed as 382 days, and led to a drastic weight loss of 276 pounds.   Fasting plays a role in many cultures and rituals and has been practiced all over the globe for thousands of years or more.  Mostly done for religious or ritualistic purposes, does it have any place in the weight loss realm?  After a day or two of fasting, people can feel foggy and cranky, but some report having clearer thoughts after more days of fasting, maybe due to increased endorphin production and release.  Although weight loss is reliably seen in studies, severe calorie restriction, or fasting on consecutive days may lead to weight loss through loss of muscle.  Intense exercise during consecutive days of fasting might even worsen the loss of muscle, since the brain and muscle tissue require a quick source of glucose, and protein can be metabolized into glucose faster than finding fuel in fat.

Fasting for many days will also quickly lead to nutrient deficiencies, and many severe medical conditions can be seen within days or weeks of intense and extended sessions of fasting.  Any fasting for longer than 24 hours, or for consecutive days should be supervised by a medical doctor, due to the possible medical complications.

What about intermittent fasting?

If full out and prolonged fasting can lead to nutrient deficiencies, muscle wasting and must be supervised by medical professionals, what about toning it down and fasting here and there, or fasting intermittently, while ensuring you're still getting adequate vitamins and minerals during your eating window?  Intermittent fasting has been studied extensively, and this is what the science says.

During rest periods, we burn carbs and fat at about a rate of 1:1.  Glycogen (sugar we store in our muscles) will last a day or two, except when we don't eat, where we turn to fat as our main source of fuel.  During alternate day fasting, where you go a full day without eating, some people will actually have increased hunger after fasting, but all the studies on alternate day fasting did still report significant weight loss, except loss of lean muscle mass has been an issue with these regimens.  Intermittent fasting regimens seem to offer additional protection against lean body mass loss, and alternate day fasting has been shown to increase LDL, the bad cholesterol.  This is something to take into consideration for anyone with cardiac disease risk factors wanting to try different regimens of fasting.

Other than alternate day fasting, different types of intermittent fasting regimens exist, depending on time spent fasting or eating.  Some suggest eating during the week and fasting on weekends, whereas some suggest fasting up to a week per month.  As explained earlier, any prolonged fasting might negatively affect muscle mass and metabolic markers, like cholesterol, and should be done under medical supervision because of the vitamin and mineral deficiencies that could appear quickly.  


Time-restricted feeding


This regimen means fasting for part of a day, but then eating in a time restricted window.  This is the regimen I feel works better with my lifestyle.  It protects against muscle mass loss, and hasn't been associated with increases in LDL cholesterol.  These regimens are easier to comply with than more prolonged fasting regimens.  They also benefit from the advantages of chronobiology.  Like we've already discussed in the Weight Loss Tips section, calories eaten at night have different effects on fat storage than calories consumed earlier in the day.  Studies where participants were told to abstain from eating after 3pm, 5pm or 9pm had more weight loss than could be explained by calorie restriction alone.  It seems that our body, metabolism and inflammatory markers benefit from taking a break from eating.  Most could advocate for a daily fast after 6-7pm, meaning that all calories are "front-loaded" earlier in the day, and then we can benefit from the upside of both chronobiology and fasting!  Personally, I often use time-restricted feeding during weekends.  Typically, I try to either not eat at all after supper, and fast until breakfast, or I eat at night, then fast until lunch at noon the next day.

Time-restricted eating seems to offer weight loss advantages, while being safe, easier to maintain and offers the additional benefits of chronobiology, where front loading your calories has less metabolic impacts than eating the same calories later in the day.  One must remember to eat a healthy variety of foods during the eating window, as to minimize any risks of vitamin or mineral deficiencies.  When in doubt, talk to your doctor!

prolonged fasting
intermittent fasting
time restricted
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