Updated: Feb 2
Humans have experienced periods of fasting for thousands of years because of food scarcity, but this pattern of eating has taken on a deliberate and structured approach in recent years. Previously, a select few exercise trainers and nutritionists recommended fasting, but now conventional doctors and specialists prescribe it as way to lose weight and gain multiple health benefits.
What is Intermittent Fasting?
Intermittent fasting is a pattern of eating that involves alternating periods of eating and extended fasting. There are generally four popular fasting approaches:
This is where you eat no food or caloric drinks for a 24-hour period.
Sometimes called daily intermittent fasting, this is where you restrict eating to certain times of the day. For example, you would eat only from 12pm to 8pm.
Alternate Day Fasting
The basic idea with this is to fast one day and then eat what you want the following day. Some people follow a modified approach where they allow a limited number of calories on fasting days.
The 5:2 Diet
This method was popularized by Kate Harrison’s book The 5:2 Diet, and it requires fasting on two non-consecutive days each week.
At first glance, fasting appears to restrict calories like any other diet. But the fasting process actually creates health benefits that many other diets don’t provide.
Fasting pioneer Brad Pilon lists the research-backed benefits of fasting in his book Eat Stop Eat as:
· Decreased body fat & body weight
· Maintenance of skeletal muscle mass
· Decreased blood glucose levels
· Decreased insulin levels & increased insulin sensitivity
· Increased lipolysis & fat oxidation
· Increased uncoupling protein-3 mRNA
· Increased norepinephrine & epinephrine levels
· Increased glucagon levels
· Increased growth hormone levels
· Decreased food related stress
· Decreased chronic systemic inflammation
· Increased cellular cleansing
Many other types of calorie restriction achieve some of these benefits, such as decreased body fat and body weight. But fasting has unique benefits, including increased insulin regulation, blood glucose management, and increased fat burning.
First, fasting can quickly and significantly reduce insulin levels. In research conducted on people who fasted for 72 hours, plasma insulin levels dropped dramatically in the first 24 hours, a more dramatic effect than all other insulin-based diets including low-carb and frequent meal timing.
Blood glucose is the amount of sugar in your blood at a particular time. When people constantly eat or overeat, the body struggles to react to the continuous supply of glucose. Over time this creates serious health consequences and can lead to conditions such as type 2 diabetes. Even a fasting period of 12 to 18 hours can help the body effectively regulate blood glucose levels.
Lastly, many people use calorie restriction as a solution for excess body fat. It’s important to understand that fat must be released from its storage space in the body in order to be burned. During fasting, the free fatty acids in the body begin to release as soon as you’re done burning the calories consumed in your last meal. This can happen between two and six hours into a fast. When you fast longer, for example 12 to 14 hours, you begin to burn predominantly body fat as a source of fuel. This results in effective fat and weight loss.
New research demonstrated the power of intermittent fasting in a study at the University of Alabama. Researchers used time-restricted feeding where participants ate all meals during an eight-hour period of the day. This was compared with another group of participants who ate during a twelve-hour period. The amount of calories consumed was the same for both groups. Both groups maintained weight levels, but after five weeks, the eight-hours group had dramatically lower insulin levels and significantly improved insulin sensitivity, as well as significantly lower blood pressure. Furthermore, the eight-hours group had significantly reduced appetite. These benefits resulted just from changing the timing of meals! The benefits remarkably increase when fasting includes the elimination of one or more meals.
Fasting and Nutrition
For people wanting to lose weight from fasting, the key is that the total calorie count of meals eaten outside of the fasting period be lower than typical non-fasting periods. Although people are usually hungry when coming out of a fast, their total caloric intake results in a lower amount than non-fasting day. In other words, people don’t compensate for the calories they avoided. As with traditional diets, calorie reduction encourages weight loss.
The process, however, is much simpler. For many people, fasting is easier to follow than most diets that require constant calorie counting. You’re simply creating a period of time with no eating, and then resume eating normally at the end of the fast.
To achieve optimal results, however, you don't get a license to eat poorly in the period of time after the fast. From a nutritional standpoint, fasting eliminates a meal or even multiple meals (depending on which approach you follow). It’s important to maintain the same nutritional intake with a reduced amount of food. Essentially you have fewer opportunities to consume the vitamins and minerals your body requires. So you need to maintain nutritional awareness to prevent deficiencies. Periodic nutrient testing is a helpful tool to ensure optimal health when using fasting.
Your decision to choose fasting should consider how well you can fulfill your body's nutrition requirements, but also the overall fit with your preferences and personality. Ultimately the method you choose should be sustainable. Benefits from any form of eating that you consider temporary will ultimately fade once you resume the previous method of eating. Research has shown that long term health and weight goals are maintained only when eating and other health habits are just that, permanent habits.
For my clients where fasting is a good fit, I make food recommendations that complement the fasting periods. It's important to come out of a fast with meals that nourish and satisfy. Combining the calorie restriction of fasting with nutrient-dense and satisfying foods creates the best scenario for people to create habits that achieve long term health goals.
Intermittent fasting is an easy and effective pattern of eating for many people looking to trim their waistlines and improve numerous health markers. With multiple fasting options, you can choose the fasting period that fits your schedule and preference. You can make the practice a habit, and there’s no need to tally daily calories.
It’s not for everyone, however. Some people prefer traditional diets where they count the calories of all the food they eat. Furthermore, people on diabetic medications, people with a history of eating disorders, and pregnant or breastfeeding women should not attempt intermittent fasting unless under physician supervision.
If you choose intermittent fasting, you should make the most of the meals you do eat to maximize nutrient intake. I encourage you to learn more about optimizing your nutrition by subscribing to my newsletter. Or, consider scheduling a free discovery call with me to discuss how I can support you.