Intermittent Fasting
It seems to be the latest ‘buzzword’ in the world of weight loss and diet, the new Holy Grail... Everyone is talking about it: Intermittent Fasting.
Intermittent fasting is an eating pattern that cycles between periods of fasting and periods of eating. Much research on intermittent fasting (IF) has been done globally, most showing promising results. Experts, however, are not saying that IF is a fad diet – rather a lifestyle habit. According to the Harvard Medical School, there is a growing body of research that suggests that when we fast is key. Dr Monique Tello says that this can 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”. Medical News Today reports that many people believe that intermittent fasting supports the body’s circadian rhythm (its internal clock), positively influencing weight loss, fat loss, as well as “the prevention of type 2 diabetes and other obesity-associated conditions”.
Let’s take a step back.
When did intermittent fasting become ‘a thing’?
Of course, many cultures and religions around the world fast. From Lent for Christians to Ramadan for Muslims, Buddhists, Jews, Hindus amongst others use fasting. According to James Clear, intermittent fasting was already being tested (albeit on overweight rodents) in 1945. Intermittent fasting might actually be an ancient secret of health, practiced throughout all of human history.
IF was made popular in 2012 by BBC broadcast journalist Dr Michael Mosley. His TV documentary ‘Eat Fast, Live Longer’ and book ‘The Fast Diet’ spurred other books – notably journalist Kate Harrison’s book ‘The 5:2 Diet’ based on her own experience, and Dr Jason Fung’s 2016 bestseller ‘The Obesity Code’.
Dr Fung is a Canadian nephrologist, and a world-leading expert on intermittent fasting. He addresses the socio-economics of obesity and combines research, clinical experience, and sensible nutrition advice. He believes that excess calories aren't the underlying cause of obesity. His book, The Obesity Code, suggests that the real issue is a hormonal imbalance in the body due to years of poor eating and consistently elevated insulin levels—one that can’t be fixed by cutting calories, fat grams, or exercising more. The solution he proposes is that for long-term, sustained weight loss, key hormones like insulin must be reset and balanced within the body.
“Despite being aware of what is “healthy”, as a society, we are getting more and more overweight every year,” says Dr Mosley. Intermittent fasting offers an evidence-based approach to weight loss and improvement of other chronic conditions because “what has long been widely accepted as “healthy eating” doesn’t actually work.”
Intermittent fasting makes intuitive – and scientific - sense.
James Clear explains intermittent fasting this way: “IF is not a diet, it’s a pattern of eating. It’s a way of scheduling your meals so that you get the most out of them. Intermittent fasting doesn’t change what you eat, it changes when you eat.”
Our bodies exist in two states - the fed state and the fasted state. In the ‘fed state’, your body is digesting and absorbing food. Generally, the fed state starts when you begin eating and lasts for three to five hours as your body digests and absorbs the food you just ate. “In this state, it’s very hard for your body to burn fat because your insulin levels are high,” explains Clear.
For the next 8 to 12 hours, your body is in a resting state until after your last meal, which is when you enter the fasted state. This is when your insulin levels are low. Only during this state can your body burn fat that is inaccessible during the fed state. In other word, says Clear, because we don’t enter the fasted state until 12 hours after our last meal, it’s rare that our bodies are in this fat burning state given that we don’t allow ourselves a long-enough break from eating.
The science of energy storage
Most of our clients only know of insulin in the context of diabetes. But it is insulin that is the key to our cell’s energy.
What we eat is broken down by enzymes in our gut, ending up as molecules in our bloodstream. Carbohydrates, particularly sugars and refined grains like white flour and rice, are broken down into sugar for energy, explains metabolic expert Dr Deborah Wexler, Director of the Massachusetts General Hospital Diabetes Centre.
Now, here’s what’s critical: sugar can only enter our cells with insulin. A hormone made in the pancreas, insulin’s job is to bring sugar into the fat cells and keeps it there. What our cells don’t use as energy is stored as fat. As long as we don’t snack between meals (which most of us do), our insulin levels will go down and our fat cells can then release their stored sugar, to be used as energy. With constant eating, our insulin levels remain high so we cannot burn off excess fat.
Dr Wexler, associate professor at Harvard Medical School, says that restricting meals to an eight to 10-hour period of the daytime, is effective to allow the insulin levels to go down far enough and for long enough.
Intermittent Fasting: How?
"Intermittent fasting is an umbrella term for an eating pattern that includes periods of fasting and non-fasting over defined periods of time," says Anna Kippen, a registered dietitian with the Cleveland Clinic. "There are different forms of intermittent fasting."
According to Medical News Today, one way of doing intermittent fasting generally involves daily fasting for 16 hours with an 8-hour eating 'window'. Basically, you eat all your meals within an 8-hour time period and fast for the remaining 16 hours. "This not only decreases our calorie intake, but also allows our gut and hormones the ability to rest between meals during our 'fast,'" Kippen says. Most people who follow the 16:8 plan abstain from food at night and for part of the morning and evening. They tend to consume their daily calories during the middle of the day. The easiest way to follow the 16:8 diet is to choose a 16-hour fasting window that includes the time that a person spends sleeping.
The metabolism slows down in the early evening and, health-wise, it is best to avoid food for 2 to 3 hours before bed. Fasting at night can make IF a more realistic, sustainable, and effective approach, not only for weight loss, but for health and disease prevention, according to the Harvard Medical School.
Another popular approach is the 5:2 plan as followed by journalist Kate Harrison. This involves following a normal, healthy meal pattern for five days a week. The other two days a week, you consume only one meal of between 500 and 700 calories each day. "This allows our body to rest as well as cut down on calories we consume as a whole throughout the week," says Kippen.
Did you know?
It was not until the 15th century that "breakfast" came into use in written English to describe a morning meal. “Breakfast” literally means to break the fasting period of the prior night.
In conclusion
Throughout human evolution, fasting has been the norm. Our ancient hunter-gatherer ancestors did not have food available year-round and they evolved to function without food for extended periods of time. In many ways, fasting from time to time is more natural than eating 6 times a day.
Research suggests that intermittent fasting may be associated with weight loss, improved cholesterol, blood sugar control and decreased inflammation. Incorporating fasting into your natural circadian rhythm certainly makes it more accessible.
As Dr Michael Eades said: “Diets are easy in the contemplation, difficult in the execution. Intermittent fasting is just the opposite - it’s difficult in the contemplation but easy in the execution.”
