Intermittent fasting. You’ve probably heard of this trending wellness concept that has grown in popularity over the past decade. From celebrities to doctors, everyone is talking about intermittent fasting. Conversations usually revolve around its effectiveness and how well people feel when they eat this way. But I remember the first time I heard the words “intermittent fasting”. I tried to block it out of my mind, writing it down as what clearly sounded like a starvation diet. If you don’t eat, you lose weight, everyone can tell you that! (Or, at least, that’s what my inner monologue tried to convince me.)
Little did I know that there is an abundance of research behind intermittent fasting. And while it may lead to weight loss, the benefits run much deeper. All eyes are on this dietary practice as research has begun to materialize around its ability to “cleanse cells”, increase longevity and reduce the risk of common diseases like diabetes and heart disease. Adding to the list, intermittent fasting keeps your DNA and cells healthy, slowing down the aging process. I would say this is the closest thing to finding the fountain of youth.
Intermittent fasting isn’t just on influencers’ radars. The method has undergone rigorous testing at research institutes, including USC’s Longevity Institute and Harvard. Interest piqued? Yes, intermittent fasting is legit, folks. Below, I’ll review the science behind intermittent fasting and point you in the right direction to start. Let’s dive into it.
Featured image by Kristen Kilpatrick.
How does intermittent fasting cause weight loss?
Let’s talk about how to focus on when you eat (and don’t worry too much about what you eat), can kick-start your metabolism, reduce your lifetime risk of serious diseases and may help you live longer. Intermittent fasting is all about burning off your sugar stores and getting to a point where your body starts burning the fat it already has stored. During a normal day, our body uses the food we eat as energy. When we fast, our body is forced to switch from burning the sugar in those regular meals for energy to burning the fat that is already there.
Neuroscientist John Hopkins Mark Mattson calls this “metabolic switching.” You’re essentially stopping fueling your body to encourage it to switch from regular running for energy to running with its fat stores. And there you have it, this is how intermittent fasting helps you lose weight.
What is ketogenesis and how does it impact blood sugar, inflammation and metabolism?
Let’s talk about ketogenesis. Our body depends on glycogen which is stored in the liver for energy to move, shake, dance and generally be alive! We get glycogen from the foods we eat, and as humans we constantly burn it just to function and stay alive. Even when we sleep, we need fuel! Over time since our last meal, these glycogen stores begin to dwindle and deplete. You may recognize the feeling of depleted glycogen stores as a “hungry” feeling. When our body begins to lack glycogen, fat cells release fat which is sent directly to the liver to create new fuel. Essentially, you are literally burning fat to stay alive. It is in this process that ketogenesis occurs. Simply put, ketones are released into the bloodstream.
This is where the magic happens. According to the National Institute of Health, “(ketogenesis) strengthens the body’s defenses against oxidative and metabolic stress and initiates the elimination or repair of damaged molecules. The impact of ketogenesis carries over to the non-fasting period and may improve glucose regulation [blood sugar]increase resistance to stress and suppress inflammation.
Ketones also send a signal to the brain to release a molecule called BDNF. BDNF is responsible for strengthening neurons and neural connections in the part of our brain that deals with learning and memory. Literal brain power!
When our body is continuously exposed to periods of fasting, we train our metabolism and our cells to be better in the future, no matter what kind of stress they are exposed to. In a world where we are exposed to oxidative stress via pollution, alcohol, endocrine disruptors and plastics, this is pretty amazing news!
What are the long-term benefits of intermittent fasting?
In a 2019 New England Journal of Medicine article that reviewed the cumulative research and evidence on intermittent fasting, Dr. Mattson discussed and gave more credence to the big claims that researchers and fanatics have made. ‘praise. Specifically, this article revealed the many benefits of intermittent fasting. This included longer life, better physical performance, and improved memory. According to Dr. Mattson, the list below is a summary of the long-term benefits of intermittent fasting.
- Thought and memory. Studies have found that intermittent fasting boosts working memory in animals and verbal memory in adult humans.
- Heart health. Intermittent fasting improved resting blood pressure and heart rate as well as other heart-related measures.
- Physical performance. Young men who fasted for 16 hours showed fat loss while maintaining muscle mass. Mice fed every other day showed better running endurance.
- Diabetes and obesity. In animal studies, intermittent fasting prevents obesity. And in six brief studies, obese adult humans lost weight through intermittent fasting.
- Tissue health. In animals, intermittent fasting reduced tissue damage in surgery and improved outcomes.
How to start intermittent fasting
Generally, people tend to follow one of two intermittent fasting routines. One is daily fasting. Many people tend to use this method because they find the daily routine more accessible and easier to stick to. During a fasting period drinking water is crucial and beverages such as black coffee, unsweetened teas and sparkling waters are acceptable. Beyond that, refrain from snacking and consuming meals as this prevents you from reaching the ketogenic state necessary for intermittent fasting to work. Additionally, research shows that it takes about four weeks to “adapt” to intermittent fasting. Note that you may feel tired, irritable, or “hungry” as your body adjusts to fasting. Eventually you will adapt and begin to reap the rewards of scheduled meals.
Daily or 16/8 fasting
The daily fasting method is usually followed by choosing a time period for fasting and one for eating. The 16/8 method is the most commonly used. Breaking down the day into 24 hours, 16 are designated for fasting and meals are eaten over an 8 hour period. Be aware that eating calorie-dense, nutrient-poor foods during your mealtime will outweigh the benefits of following an intermittent fasting routine.
Although you can structure the 16/8 method however you like, ending your eating window after 6 p.m. can be a helpful way to achieve a more normal balance while fasting. It might look like finishing your last meal of the day at 6 p.m. and having your first meal the next morning no earlier than 10 a.m. Between 10 a.m. and 6 p.m., you can eat normally without restriction.
Bi-weekly fasting or 2/5 method
This method involves five days of normal, healthy, unrestricted eating, followed by two days of restricting your calories to around 25% of your daily needs. That equates to just about 500-600 calories, two days a week. This can easily be achieved by fasting all morning, then eating a large, satisfying breakfast, followed by a light filling snack in the late afternoon. You would then fast again until the next morning, when you return to a normal eating day. Many people use Mondays and Thursdays as fasting days.
Who should not fast intermittently?
It’s a good idea to see a doctor to make sure intermittent fasting is safe for you, especially if you have any underlying medical conditions. People with or who have had the following conditions should not fast intermittently:
- Children and adolescents under 18
- Pregnant or breastfeeding women
- People with diabetes or blood sugar problems
- Those with a history of eating disorders