The Ultimate Guide to Intermittent Fasting (Part 2)
Intermittent fasting (IF) is well studied for short-term weight loss, and there’s some emerging animal research to suggest that IF may also be able to reduce oxidative stress and free radical damage, improve cognition, performance and productivity, delay aging, provide an anti-inflammatory benefit, and benefit gut microbial diversity.
But there are many different ways to IF, and it’s important to find the right type of IF for you. Read on to learn about…
- How long you need to IF in order to see the benefits
- The different types of IF and their benefits
- How to find the type of IF that’s best suited to you
- The IF type that’s best suited to weight loss
- Including how your DNA can predict the results you see on an IF protocol
- Why consuming enough quality protein at meals is essential to your success
IF is also known as intermittent energy restriction or intermittent calorie restriction. IF is a general term under which several forms of cyclical fasting fall, and these various fasting diets are highly variable in terms of how long we fast for, or how long a time window we have to consume food (calories).
By definition, IF is about the restriction of foods, while consuming foods only in a specific time period, or window. The amount of time we restrict foods however, varies depending on the source, and so many people are “doing IF” in many different ways:
Alternate Day Fasting (ADF)
Alternating “Fast” and “Feast” days. On Feast days, food consumption is based on hunger. On Fast days, a caloric intake of less than 25% of normal caloric intake is consumed. ADF is absolutely not appropriate for Type-1 Diabetics, women who are pregnant or breastfeeding, those managing disordered eating, or those who require regular food intake to take medications.
Periodic Fasting (PF) or Intermittent Calorie Restriction (ICF)
Fasting for up to 24hrs once or twice per week with no measured caloric intake on other (non-fasting) days is most commonly practiced as a form of religious fasting.
Time Restricted Fasting (TRF)
Perhaps the most common trend in urban professionals, TRF establishes a feeding window throughout each day (usually 6-10hrs) with a 14-18hr daily fast.
Generally, IF has not been shown to be harmful physically or mentally (i.e. mood) in humans who are of normal weight, overweight or are obese.
Most studies in both humans and animals have shown that IF is an effective strategy for weight loss in the short-term, but have not yet established any improvements in long-term weight loss maintenance[i]. Weight lost on IF diet plans are likely still susceptible to rebound weight gain.
There is no conclusive evidence to suggest that any form of IF is superior to others in terms of weight loss, fat loss, metabolic or physiological benefits at this time. When using TRF, I notice that my patients get the most benefits when they fast for 16hrs or more (with an 8hr feeding window). Most people on this regimen will essentially skip breakfast (except perhaps for a black coffee) while fasting from approximately 8pm until about 12pm the next day. It may be easier to think of this as a feeding window between 12pm and 8pm.
14hr TRF (with a 10hr feeding window) seems to be the most convenient for most people as they can still have a breakfast and most people can sustain this without getting hungry. This usually looks like finishing dinner by 7pm; eating no snacks or dessert, and then delaying breakfast until they are at the office in the morning.
Pro Tip: Make sure you’re getting lots of protein in your meals, no matter what form of IF you’re doing. This will help to minimize the hunger pangs and continue to boost your metabolism. And skip the dessert, an influx of simple carbohydrates right at the end of a healthy meal is a great way to make your blood sugar levels go on a rollercoaster ride and lead to hunger and poor sleep.
Genomic Medicine: Is Intermittent Fasting Right For You?
When determining the best treatment recommendations for my patients as a Naturopathic Doctor, I’m always considering the compliance factor. How likely is it that you will be able to execute and maintain or sustain this plan? One way we can assess your likelihood of being able to sustain an IF style diet is through genomic testing and finding out what your DNA is telling us: the MC4R gene is related to obesity and appetite. If you have raw data from your 23andme or Ancestry results for example, you can determine which version of this gene you carry.
The TT allele combination is considered the typical (wild) gene combination. But if you have the CC or CT variant of this gene, you’re more likely to have a lowered BMR, increased insulin levels, increased hunger and a tendency to snack more often. The irony here is that you would very likely benefit from IF, but that you’d have a really hard time of executing, and maintaining the regimen. High fat diets (eg. Ketogenic diets, often associated with IF), also seem to cause MC4R CC or CT carriers to overeat, they’ll eat more of that meal, and after even a single high-fat meal it may increase your likelihood of overeating for up to two weeks afterwards!
Bottom line, when considering IF: Think about what type of IF plan would work best for you in terms of your ability to sustain it or at least 12 weeks (where most studies have shown benefit for weight loss), and how it might impact your life mentally, physically, socially and in terms of work. If you have had genomic testing done, consider asking your informed doctor about determining your allele combination for the MC4R gene.
Questions about IF
Should women fast? Does the IF window differ if you’re a man or a woman?
There’s less data for women specific to Intermittent Fasting, and there is a suggestion IF may affect women’s hormones differently from men. Specifically, some women cite changes or interruptions to their menstrual cycles when undergoing an IF regimen. There is some human data to support this thus far, but the effects in women for things like iron, protein, and fat deficiencies are likely to be more noticeable in women via the menstrual cycle, and taking on an IF regimen may simply be exacerbating those deficiencies when it’s not done correctly or healthfully. Just like any dietary plan, it’s still imperative that we get adequate macro- and micronutrients, even if that means we’re doing it in a specific window of time throughout the day.
I’ve heard that skipping breakfast correlates with gallstones. Is this true?
Generally speaking, there is some data to suggest that skipping meals may be correlated (but not necessarily cause) gallstones. But gallstones are caused primarily by LOW bile production. Bile production is stimulated by fat consumption (especially saturated fats), and depleted production is associated with high carbohydrate consumption. In IF, bile is concentrated, and if you’re either combining IF with ketogenic diets (typically higher in fat) or at least consuming adequate fat in the diet, there should not be concern that IF should be causal for gallstones.
What’s more effective—skipping breakfast or skipping dinner?
The most important thing is a schedule that is conducive to consistency and routine! A plan that isn’t going to be executed regularly isn’t going to be successful at all.
IF is not a one-size-fits-all approach.
Choosing the right type of IF depends on a number of factors, including your health, your lifestyle, and, of course, your goals.
But what about how to IF to see benefits? Can you have bulletproof coffee when fasting? What about coconut oil?
In the final part of The Ultimate Guide to Intermittent Fasting, Dr. Marr clears up the confusion about what you can and can’t have when on a fast—once and for all. He’ll also share how to properly break a fast (including which supplements to use) and will share his weekday fasting protocol.
[i]Patterson RE, Sears DD. Metabolic Effects of Intermittent Fasting. Annual Review of Nutrition 37:371-93.