Intermittent fasting and weight loss: Does it work?
With an increasing obesity epidemic comes the search for effective weight loss strategies. One of the more recent strategies to gain attention is called Intermittent Fasting, or IF for short. Google searches for “Intermittent fasting” have skyrocketed in the last couple years, now approaching almost 1 million searches per month! It is clear that people are becoming more and more interested in learning about intermittent fasting (IF), also called time-restricted feeding.
While there are many claimed benefits of IF (anti-aging, anti-cancer, anti-inflammation, etc), this article will mainly focus on its potential benefits for weight loss. Is it a fad, or can it be an effective strategy for losing weight. Let’s take a look!
You will still hear people, nutrition professionals included, recommend eating every 3-4 hours so that your metabolism spikes throughout the day and you burn more calories. So what is best then? Let’s take a look at what the science says and then you can decide what might be best for you and your lifestyle.
What is Intermittent Fasting?
Before we talk about how IF can help with weight loss, it is important to understand exactly what it means. Simply put, IF is an eating pattern where a person cycles between periods of eating and fasting. It has roots in traditional fasting that has been practiced by people around the world for centuries, often times for religious purposes.
IF doesn’t outline what you should be eating, but only when you should be eating. There are many different protocols you can follow, but here are the most popular...
16/8 Method- This is likely the most common. It involves choosing an 8-hour “eating window” where you consume all of your calories for the day. For example, eating between the hours of 12-8 each day. It is important to note that you do not consume calories from anything, including liquids.
5:2 Method- This method is where a person will eat normally for 5 days of the week, and then fast for the other 2. People who follow this method often still consume some calories on their fasting days (less than 500/day).
Alternate day fasting- In this method, people follow a 24-hour fasting period with a 24-hour feeding period. Because fasting for 24 hours is difficult for many people who have never fasted before, many will start with the 16/8 method and slowly incorporate longer and longer fasts.
How can Intermittent fasting help me lose weight?
It’s a matter of time. The main reason intermittent fasting works for weight loss is the fact that you have fewer hours in the day to consume calories. When it comes to weight loss, calories are king. Unless you overcompensate during the feeding window, it will be more difficult to eat the same amount of calories in a shorter time frame.
In regards to long term success, the best diet to follow is always the one you are most likely to stick to. One of the pros of IF is that the rules are easy to understand and avoiding confusion is very important when it comes to weight loss.
Take the keto diet for example. Confusion often occurs around this diet because getting and staying into nutritional ketosis may have different requirements for different people. If you do not have a nutrition professional to guide you, this can be a very frustrating experience.
Here are some ways that that IF can help in your diet adherence:
Simplicity- From my experience with clients who choose to try IF, one thing they often note is that it makes eating more simple. Eating less meals per day eliminates many decisions around food, and there are MANY decisions each day to be made.
Time-saving- Can you remember a time when you were busy with something and then it came time to eat? Advocates of IF like the idea of eating less often because they have more time in the day to do other things.
Flexibility- One of the best parts of IF is that there is no one size fits all approach. You can choose whatever feeding window you want and whatever foods you want. You can choose to follow it during the week and then on weekends go a little more relaxed. Flexibility is key to long term success.
How does Intermittent Fasting affect my hormones?
Insulin- When we eat, insulin is released to signal to the body that food is present and we need to do something with it, shuttling the calories into all types of cells (including fat cells). When we fast, insulin decreases significantly, forcing your body to take fuel from stored body fat.
Growth hormone- This one peaks in the middle of the night when you are naturally fasted and helps with growth and repair. It also increases fat burning because you aren’t consuming calories while you sleep but also aids in maintaining lean muscle. When you fast for longer periods, this stays elevated longer.
- Ghrelin- This hormone is also called the “hunger-hormone”. Your body will release ghrelin around the eating schedule you have probably had for years...breakfast, lunch dinner, snacks, etc. However, ghrelin levels will follow this pattern even if you don’t eat, meaning that you can retrain your body on when it should expect food. Over the first couple weeks of IF, you will be hungry as your body adjusts to a new eating schedule.
Is Intermittent fasting safe for weight loss?
Think about the word breakfast for a second. What does it actually mean? By eating food after you wake up, you are “breaking the fast”. Therefore, you actually perform IF on a daily basis without even realizing it. So yes, it is safe. However, many people become interested in IF because they want to lose weight. And we know that obesity and carrying that extra weight can increase your risk for other negative health outcomes.
People with the following health conditions should refrain from IF, unless under the supervision of doctor:
Diabetes- if you already have complications managing your blood sugar, IF could make things worse, especially if you are insulin resistant and/or take medications for managing your blood sugar.
Have medications you take daily that require food
Pregnant or breastfeeding- Babies need food too.
If you do not have any of these health conditions, still check with a health professional before starting IF. But remember, it is okay and normal to feel hungry at times. In general, people are not in tune with their internal hunger cues and often times we eat when we are not actually hungry (think boredom eating).
What do I eat with Intermittent fasting?
One of the reasons there is so much appeal around IF is that there is a lack of food rules. While it may sound tempting to eat whatever you want while doing IF, the benefits are not likely to come if you choose to eat Big-Macs and milkshakes all day.
For obvious health reasons, I still recommend sticking to a whole foods diet whenever possible. This goes whether you choose to follow IF or not. But because you will be restricting calories for weight loss, you will get the best bang for your buck in terms of calories by eating foods that are filling and nutrient dense, for example:.
Quality complete protein sources like eggs, meats, fish, etc.
Fruits and vegetables, especially the ones higher in fiber.
Healthy fats like avocados, nuts, full fat dairy, etc.
If I want to try Intermittent Fasting, how should I start?
For most people, it is best to start by taking your normal breakfast time and delaying that a couple hours. After you feel that you have adjusted enough to this delay, you can slowly work your way up to the 16/8 protocol and then experiment from there on what time frame or protocol you like best.
Remember, the key is to be sure you aren’t consuming calories from any source during your fasting window. Check the nutrition facts on anything you consume, including liquids. Anything that has calories will take you out of the fasted state.
Stick with it for a few weeks before you decide if it is for you. It can some time for your body to adapt to a new eating style, especially if you have eaten the same way for most of your life.
Exercise is still important, especially strength training. You will be in a calorie deficit and losing weight so it is important that you are stimulating your muscle tissue so that you are able to maintain as much of it as possible during your weight loss journey.
Bottom line: Intermittent fasting can be a great tool for managing calorie intake. However, it is just one approach and may not be for everyone. The clinical research is still in its infancy and still needs more robust longer-term trials before anyone should claim it is the best diet for everyone.
Remember to talk to your doctor and nutritionist/dietician before starting any weight loss program. The key to your dieting success will still be determined by your calorie intake. You will feel hungry for the first couple days/weeks as your body adapts to a new eating pattern.