What is intermittent fasting?
An effective option for managing weight and hormones is intermittent fasting (IF).
The “fasting” portion of IF refers to the time between meals when you’re not eating. Depending on the type of IF you choose, this can vary greatly – from a matter of hours to a full day. Of course, continuously fasting day in and day out isn’t healthy for your body, and that’s where the “intermittent” part comes in. In short, IF is a type of eating pattern that specifies times for eating and times for fasting.
Some people might refer to IF as a diet, but since you can consume whatever type of food you like, it doesn’t really fit the definition. As long as your meal times fit into the timing specified, you are properly following IF.
Let’s take an in-depth look at the different health benefits you can expect from intermittent fasting.
Benefits of Fasting
After food is consumed and metabolized, what remains is the smallest functional units of nutrients – fatty acids, glucose, and amino acids. These tiny nutrients then enter the bloodstream. Glucose is the key to most of the benefits of intermittent fasting. If glucose is not used for energy, it will be stored in cells as fat, and this process requires insulin. When intermittent fasting is followed correctly, circulating glucose levels should decrease, and the need for insulin will decrease accordingly. Decreased circulating insulin prompts fat cells to release stored glucose which produces energy, leading to weight loss (2).
Intermittent Fasting can also assist in weight loss by increasing the body’s metabolism. Lean muscle loss is also spared more effectively with IF than a pure caloric deficit, with some studies showing as much as 4 to 8 percent weight loss and 11 to 16 percent body fat loss in as short as 3 weeks of intermittent fasting (3). Overall calorie restriction is still necessary in order to lose weight, but by including IF, results can be obtained much more efficiently.
Beneficial hormonal changes take place relatively quickly once IF has started. Some of these include:
• Levels of Human Growth Hormone (HGH) can increase by as much as 500 percent (4, 5, 6, 7). This can be extremely valuable if weight loss is the goal of IF, as higher levels of HGH can help the body lose fat and build muscle more easily.
• As noted before, circulating insulin levels decrease, which may also provide weight and fat loss benefits. Circulating levels of norepinephrine (noradrenaline) also drop, which also may promote fat burning by prompting increased metabolism (8).
Aside from weight loss, intermittent fasting has the potential for several health benefits:
• In type 2 diabetics (as well as those who are overweight or obese and non-diabetic), IF can provide increased insulin sensitivity, which can in turn decrease fasting blood sugar and insulin levels – in short, improving glycemic control (9, 10, 11).
• As little as 2 weeks of intermittent fasting can improve symptoms and prognosis associated with disorders such as asthma, allergies, and autoimmune diseases (12).
• IF can also decrease the risk of developing heart disease by decreasing systemic inflammation and reducing triglyceride levels (13, 14).
• By reducing systemic inflammation, IF can also decrease the risk of developing or decrease symptoms associated with chronic diseases such as asthma (15, 16).
• Intermittent fasting even shows promise in animal studies to prevent several types of cancer, including breast, brain, and liver cancer, lymphoma, and melanoma (17, 18, 19, 20).
Is intermittent fasting right for you?
Just like every other lifestyle change, IF isn’t for everyone. So, how do you decide whether it’s appropriate for you, your health concerns, your goals, and your lifestyle? There are several factors to consider.
First, consider whether your gender might play a role. Some research has shown that IF tends to be more effective for men compared to women. The scientific basis for this discrepancy has not yet been pinpointed – but it appears that changes in insulin sensitivity are more noticeable in men than women (21). Intermittent fasting may also prompt hormone imbalances and issues such as infertility and menstrual disturbances (22, 23). However, if you are a woman, you can still certainly be successful with IF. Starting slowly and paying attention to your body may be good strategies to follow.
Additionally, existing health conditions should be taken under advisory. For most people with any type of health condition, IF will likely be appropriate. However, you should always check with your doctor prior to starting IF. If you are taking any medications, determine if you need to change timing for any of them when following a different meal schedule. If you take medications that must be taken with food, certain types of IF (those that have a shorter fast) will be more appropriate for you than others (those that include entire days of fasting).
So, who should try IF? In general, most healthy people can successfully gain health benefits from it. However, if you have a history of disordered eating or a diagnosed eating disorder, you should not start IF. Intermittent fasting is also not appropriate for underweight people, those with nutritional deficiencies, or those with type 1 diabetes. Children, adolescents, pregnant women, and those who are breastfeeding or trying to conceive should also avoid IF.
If you do not have any contraindications to starting IF, it is recommended that you get a simple blood test prior to beginning. Your goals and health condition dictate which tests would be important in your situation and can be done with your family doctor or a functional medicine expert at our office. We also recommend retesting your target values after three months to make sure you’re on track to reach your goals.
Types of IF
If you’ve decided to give IF a try, your next step is to decide which type to follow. There are several different types – some of the most popular are 16:8, 12-hour fasting, 5:2, alternate-day fasting, and the Warrior Diet.
In 16-hour (also known as 16:8) IF, your goal is to fast for 16 hours, then eat only during an 8-hour time window. The same pattern is followed every day. Although this might sound difficult, it actually tends to be the easiest for people new to IF, and it requires the least planning in order to succeed. If you think about it, it’s quite close to what most people consider a “normal” eating pattern to be, and many 16:8 IF’ers find it to be sustainable long-term.
Typically, the best way to structure 16:8 IF is to begin your fast after dinner and skip breakfast. You’ve probably been told over the years that skipping breakfast is bad – and this certainly can be true – but only when you fail to make up for it in a nutritious way later in the day. If you skip breakfast in order to eat a huge fast-food lunch and dinner, that’s obviously not going to do the trick. However, if you eat sensibly for the rest of the day, skipping breakfast is not going to hurt. 16:8 IF does not require special foods, detailed macros, or extremely-restrictive calorie intake.
A typical meal schedule for 16:8 IF might look something like:
• Fast from dinner the night before (finished at approximately 7pm)
• Morning Snack – 11am
• Lunch – 1pm
• Afternoon Snack – 3pm
• Dinner – 6pm
• Fast again until morning snack the next day (11am).
By following a schedule such as this, you can still enjoy breakfast foods as part of a morning snack if you really enjoy them. If you’re not much of a breakfast person, you can always start your day with lunch and finish the 8-hour window a little later in the day. If you’re not a snacker, you can eliminate those and simply enjoy 2 or 3 moderately-sized meals instead. 16:8 IF can be adjusted in many ways to fit your lifestyle – even if you do shift work or work nights!
As you can see, 16:8 IF could be ideal for someone who struggles with nighttime snacking. By “closing” the kitchen after dinner each night, the option is no longer there. Even if you don’t have this problem, going to bed without a full stomach weighing you down tends to help improve the quality of your sleep.
Just like 16:8 IF, 12-hour fasting requires you to stick to a certain eating window each day. In this case, it’s a bit more liberal – with only a 12-hour fast and a 12-hour window to consume your food for the day. 12-hour fasting is even more in line with most peoples’ eating habits, and like 16:8 IF, it can be extremely helpful if you’re a night eater. Since the fast is shorter, if you begin fasting early enough in the evening, you can enjoy your breakfast right on schedule in the morning.
A typical meal schedule for 12-hour fasting could be:
• Fast from dinner the night before (finished at approximately 7pm)
• Breakfast – 7am
• Lunch – 12pm
• Afternoon Snack – 3pm
• Dinner – 6pm
• Fast again until breakfast the next day (7am).
As with 16:8 IF, the timeframe is completely flexible, so if you prefer to enjoy an evening snack and skip (or have a late) breakfast, that is perfectly allowable.
Although the name looks quite similar, 5:2 IF is very different from 16:8. In 5:2 IF, you eat “normally” on 5 days of the week, and your “fast” consists of 2 days of very low food intake. Depending on how strict you want to be, fasting days generally range from 20 to 25 percent of your usual intake, which usually amounts to about 500 to 800 calories (24). That said, 5:2 IF tends to be more difficult to follow, as caloric intake that low can make you quite hungry.
As with 16:8 IF, no special foods are required or restricted. Most people following 5:2 IF prefer to consume 2 to 3 small meals on their 2 fasting days in order to maintain a normal eating schedule and feel less deprived. Oddly enough, the most important factor in success on 5:2 IF is a normal intake on non-fasting days. Many people are tempted to chase one of two extremes – either by continuing to restrict food intake on non-fasting days or simply overindulging on those days.
Additionally, you’ll want to make sure that you schedule your low-calorie days appropriately. The two fasting days should not be consecutive, and if you exercise, it’s probably best to schedule those two days as rest days. Also take into consideration whether or not you would want to fast on weekend days – most people do not.
Alternate-day fasting (ADF) can essentially be thought of as a step up from 5:2 IF. On this type of IF, the “fasting” (20 to 25 percent of usual calories) days occur every other day. For instance, you might fast on Tuesday, Thursday, and Saturday. The most common type of ADF is actually a modified version, as strict ADF involves true fasting every other day. As you can imagine, this is not reasonable for most people, hence the more realistic modified version (25).
Alternate-day fasting is typically useful for people looking to lose weight but tends not to be sustainable in the long run, as low intake on such a frequent basis can feel very restrictive and difficult to maintain.
However, if you can stick to the plan for a substantial period of time, this type of IF does have strong research to back up its efficacy in terms of both weight loss and health benefits. Studies have shown that hunger on fasting days tends to decrease within the first 2 weeks of following ADF, an effect believed to be due to changes in the hunger hormones ghrelin and leptin (26, 27). When it comes to weight loss, many people find that ADF feels more natural than simply reducing their calorie intake on a daily basis.
As the name implies, this is a quite challenging meal pattern. Followers of the Warrior Diet “fast” during the day (fruit, vegetables, and liquids only) and “feast” (consuming a very large meal) at night. Typically, you must adhere to a 4-hour window for eating, and a Paleo diet is recommended.
How to implement basic intermittent fasting
As far as diets or lifestyle changes go, implementing IF is rather simple. You don’t need to purchase any specific or branded foods, learn new preparation techniques, or cut entire food groups out of your diet. If you don’t usually feel hungry when you wake up, the transition to IF (especially 16:8) may be very easy for you.
That said, most people will find it most comfortable to start with either 12-hour fasting or 16:8 IF. If you wake up hungry and enjoy breakfast, 12-hour fasting may be the better choice for you.
Eventually, you may find that you’re hitting a plateau or you’re not making any more progress. You can either adopt a stricter approach (such as fully fasting on fast days for 5:2 IF) or switch to a different type of IF. There are no specific guidelines as to when you can change to a more advanced regimen, so just go by how you feel. You should know when you are ready to move forward.
How to lose weight without losing your mind
Depending on the type of IF you choose, it can be difficult and stressful. You may feel like giving up, but be sure to find something that motivates you. Whether it’s a weight goal, improving your health, or being around longer for your family, focus on your inspiration when things get difficult and hunger threatens to derail your plans.
To stay in the right mindset, different things will work for different people. If you’re religious or spiritual, prayer or meditation may provide a useful outlet for you. If you are neither, perhaps yoga or music can help you escape on a tough day. Many people find that therapies such as acupuncture can help regulate hormones and control appetite while on IF. Checking in with your functional medicine expert on a regular basis can help you work through any roadblocks.
Common rookie mistakes to avoid
For starters, you will likely feel tempted to overindulge during your non-fasting times, regardless of whether these times are hours or days. If you spend this time “catching up” on the food you couldn’t consume during your fast, your weight loss will be hindered. In order to avoid this, be sure to maintain a reasonable diet during your non-fasting days.
Another common mistake is trying to change too much too fast. When starting IF, you may be tempted to try a new diet such as keto or vegetarianism. However, in order to get the best results from IF, you don’t need to change what you eat – it’s all about when you eat it. Following a generally healthy, balanced diet is your best bet. Lean meats, fresh fruits and vegetables, whole grains, and dairy should be prioritized over snack foods and empty calories.
Additionally, don’t fall into the trap of failing to stay hydrated. Fasting does not imply that liquids are off-limits. In fact, adequate fluids can help you feel better during your fasting periods. Calorie-free beverages such as coffee, tea, and water are ideal, but try to avoid adding sugar (milk or cream are fine).
Finally, do not make the mistake of simply changing your diet and not incorporating exercise. If you want to maintain sustainable weight loss as a result of IF, resistance exercise can help you to build muscle rather than lose it while dropping weight. Make an appointment with our physical trainer to develop a personalized workout plan and learn proper form to maximize results.
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