Intermittent Fasting:  How It Can Be a Useful Tool for Weight Loss

Intermittent Fasting can be a useful tool to support disease reversal, longevity and weight loss. Leaders in the field like Valter Longo, PhD. have written and spoken about the benefits of intermittent fasting on weight loss, disease reversal and aging. Dr. Longo is the Director of the Longevity Institute at the University of Southern California and author of the book, The Longevity Diet,⁽¹⁾

What is intermittent fasting?

Intermittent fasting is a voluntary window of time when you do not eat or drink except for plain water, tea, or coffee.  Essentially you are giving your digestive system a rest during this window.  Humans have always intermittent fasted to some degree because there were periods during our evolution when food was scarce. We had no choice but to eat when food was available. 

Additionally there is a natural fasting window when we are sleeping.  At night the body uses this time when it is not digesting food to repair itself.    

How long should we fast?

Fasting has been used for thousands of years. It is practiced for its spiritual and health benefits, but it has only been scientifically studied more recently.   According to Dr. Longo, current data suggests that the safest timeframe to fast is a 12-hour window.  This means that you eat within a 12-hour time slot, such as between 6 a.m. and 6 p.m., and avoid eating within 3-4 hours of bedtime. This window will give your body time to rest, and for insulin levels to fall. Insulin is our bodies fat storage hormone that is secreted after we eat. It takes sugar from our bloodstream and stores it in our fat, liver or muscle cells. When insulin is low our bodies burn fat for fuel.

Some people choose to extend their fasting period to 14 or 16 hours. As an example, they eat between 8 a.m. or 10 a.m. and 6 p.m.  Still others choose an alternate day fast of skipping eating or reducing calories significantly every other day.  Further, some ascribe to the 5:2 diet, which is a pattern of eating normally for five days of the week, but then restrict food intake to just 500 calories on the two fasting days.

Dr. Longo’s Advice

Don’t skip breakfast. According to a recent article by Healthline, “While research hasn’t found an exact connection, studies indicate that people who skip breakfast tend to have much higher rates of cancer, cardiovascular disease, and death. They’re also more likely to have worse heart and overall health as well.”

Dr. Longo says “if you’re going to skip a meal, make it lunch or dinner, and definitely nix snacking before bed. Breakfast doesn’t have to be a big ordeal. If you typically wait until midday or later to eat because of time or convenience, it’s easy to incorporate a light breakfast of tea or coffee, plus toast with preserves, into your morning routine.”⁽⁴⁾

Is fasting right for everyone?

No.  It is generally not recommended for pregnant or breastfeeding women, children or adolescents to practice intermittent fasting.  Our bodies are undergoing a lot of change during these periods so fasting is best to be avoided without medical supervision. 

It is also not recommended for people with certain conditions, such as diabetes or people who take medications for blood pressure or heart disease who may be more prone to electrolyte abnormalities from fasting. 

It is also not a good idea for anyone who suffers from body dysmorphia or other psychological or mental health issues.

You should always consult your doctor before considering any type of restricted eating program.  

Does Intermittent Fasting (IF) work for weight loss?

Research on Intermittent Fasting (IF) to date has primarily been done in animals or in small group human studies.  According to an article published in February 2021 by Harvard Health, “Studies in humans, almost across the board, have shown that IF is safe and effective, but really no more effective than any other diet.”

Depending on the type of fast that you choose, it can be difficult to adhere; however, “a growing body of research suggests that the timing of the fast is key, and can make IF a more realistic, sustainable, and effective approach for weight loss, as well as for diabetes prevention…especially when combined with a nutritious plant-based diet.”⁽²⁾ 

An article entitled “What is Intermittent Fasting and Does it Really Work? ⁽³⁾ published by the New York Times, stated “There is some new evidence that shows different forms of fasting are not equal — in part because some are easier than others, but also because some forms of fasting better match our body’s natural circadian rhythm, thus lowering insulin levels, increasing fat-burning hormones and decreasing appetite.  Basically, because our metabolism has evolved to digest food during the day and rest at night, changing the timing of meals to earlier in the day may be beneficial.”

The bottom line for weight loss is that it can be as effective as other calorie restriction diets if sustained.  Over the longer-term the most promising fast seems to be the one that works with our circadian rhythms. An overnight window starting in the early evening appears best. This gives our bodies insulin a chance to drop and fat burning to occur causing us to essentially lose weight while we sleep. 

Are there other health benefits besides weight loss to IF?

Yes. Fasting does more than help us burn calories and lose weight. Researchers reviewed dozens of animal and human studies to determine that it can improve metabolism, lower blood sugar levels, reduce inflammation (which can benefit a host of inflammation related issues from arthritis to asthma).⁽²⁾  It also helps with a process known as autophagy, which is our bodies way of removing damaged cells.  Fasting has even been shown to lower cancer risk and enhance brain function.⁽²⁾      

Conclusion

Intermittent Fasting (IF) can be as effective as other calorie restriction programs and a useful tool for weight loss.  It also has a host of other benefits to human health.  The most common type of IF, and likely the one that is most sustainable for long-term weight loss is the overnight fast, which starts 3-4 hours before bedtime.  This type seems to align best with how our bodies evolved giving us time to rest, repair and burn calories!  

Sources:

1. https://www.valterlongo.com/daily-longevity-diet-for-adults/
2. https://www.health.harvard.edu/blog/intermittent-fasting-surprising-update-2018062914156
3.  ttps://www.nytimes.com/2019/11/23/style/self-care/intermittent-fasting-benefits.html
4. https://www.healthline.com/health/food-nutrition/intermittent-fasting-tips#6.-Dont-skip-breakfast