Another January has come and gone, and likely so too have some new years resolutions. For those of you still looking for the best quick weight loss solution, you may have been considering the Intermittent Fasting (IF) diet. While not new, Intermittent Fasting definitely has gained some momentum over the past year and here at Abbey’s Kitchen, we wanted to set the record straight on what it means for you and your weight loss goals.
What is Intermittent fasting?
As you can probably guess from the name, the Intermittent Fasting diet involves a fast, but it’s the “intermittent” part that sets this fast apart from the annual religious fasts you may have partaken in at some point in your life. In most intermittent fasting diet regimes, you have a smaller time window when you can only eat (usually fewer than 8 hours), and you fast for the remainder of the day. These fasts are longer than a typical “overnight fast” (when you’re sleeping), and range from 16 hours to a maximum of 1.5 days (but usually no more than 24 hours).
In short, Intermittent Fasting is a broad term for various diets that involve cycling between a fasting period and a non-fasting period.
You may be thinking, “I’m not a really big fan of having less time to eat. I’m already busy and rushed enough as it is!”
Just wait! Many have claimed that Intermittent Diets that involve prolonging this fasted state have a multitude of health benefits such as improving glucose homeostasis, boosting energy, increasing growth hormone (GH) production, reducing inflammation decreasing oxidative stress, lowering triglyceride (TG) levels (here and here) and blood pressure, increasing and protecting brain function (here, here) increasing resistance to age-related diseases like immune disorders, cancer, heart disease, stroke, eye disease, Alzeimer’s (here, here) and promoting longevity!
Wow. Now THAT’S really a LIST. But are all of those Intermittent Fasting claims true?
Well, a lot of those claims have been made based on animal studies. And of course, although rodents like Ratatouille are clever ones, a rat’s body and a human’s body don’t work the same way, and it’s harder to conduct those studies on humans due to many influencing factors. The ones that do exist out there are pretty limited, but do show some exciting results that puts IF out there as a possible approach to benefiting human health as well! But it is important to mention that sometimes these studies had mixed results, so we can’t make super clear cut conclusions.
Most Common Types of Intermittent Fasting
Generally, Intermittent fasting involves restricting calories 1-3 days a week and then being able to freely eat on ad libitum days (days where you can eat as you wish or without restriction!).
There are different styles of Intermittent Fasting programs out there, with the most popular ones being Alternate-day fasting, Whole-day fasting and Time-restricted feeding. Let’s take a looksy at each.
This type is the most-studied form of intermittent fasting, which requires alternating between feeding and fasting days. On a typical fasting day, there is 1 meal at lunch that consists of approximately 25% of caloric needs based on the individual. This form of fasting involves “modified fasting” which has different durations/periods of fasting from anywhere between 30-40 hours based upon the individual’s schedule.
Compared to alternate-day fasting, this kind of fasting may seem “more extreme” to some because out of 1 to 2 days per week, you need to either severely restrict your calories or completely abstain from food. This is commonly known as the “5:2 diet” in which the 5 represents the number of ad libitum days you eat normally, and the 2 represents the number of nonconsecutive days you have to restrict calorie consumption to 25% (500-600 calories) of your total daily energy expenditure calories.
This is the most “lenient” (if you want to call it that) type of Intermittent Fasting that requires you to fast for a specific number of hours each day. A very popular form of this time-restricted feeding program consists of an “under-eating” phase that lasts for 20 hours, followed by an “overeating” phase lasting for 4 hours that takes place every 24-hour period. This form of fasting is followed as a type of routine.
Of course, it’s important to consider both the PROS and CONS of something so new like Intermittent Fasting, so let’s go through them together.
PROS of INTERMITTENT FASTING
1.PROMOTING Health & Weight Loss
Results in several human studies have found that alternate-day and whole-day Intermittent Fasting has been associated with a significant DECREASE in body weight, body fat, and waist circumference both short and long term, but has also been frequently observed in some time-restricted IF studies.
Like with any diet, however, some of the weight loss may be lean muscle mass, as well. But it’s been observed that with intermittent fasting, individuals can lose fat mass while RETAINING MORE of their lean mass (aka. our fat-burning lean muscle!) compared to daily calorie restriction-type of diets.
Also, Intermittent Fasting may help improve the symptoms of individuals with asthma by lowering airway resistance, oxidative stress and inflammation.
Not to mention, researchers found improvements in insulin sensitivity, improvements in glucose homeostasis, as well as significant DECREASES in total cholesterol and LDL (the artery-clogging, BAD cholesterol!), blood pressure and triglyceride levels, which is super important for preventing and reducing the risk of various diseases – notably, cardiovascular disease (in normal weight, overweight and obese individuals)! (here, here, here, here, here).
2.BRAVO to Increased Brain Functioning!
Other studies have explored the powerful effects of this time-restricted diet on cognitive performance (such as memory), which has been found to be beneficial especially for athletes whether they are exercising or at rest (here, here) .
3.No calorie restriction and No change in diet?!
That’s right! You can still eat the same number of daily calories and don’t have to take away or change the actual foods you eat (even though we believe you would reap MUCH BETTER results for your health with a whole-food, well-balanced diet from each of the 4 food groups).
This eating pattern is easily implemented and for those who like routine, it can be adhered to fairly easily (compared to the traditional calorie restriction that may be hard to follow in the long-run)! For some people, it may be easy to incorporate into your current routine and you don’t have to worry about limiting the types and amount of food you eat on feasting days. For example, did you know that the common “Time-restricted feeding” type of Intermittent Fasting is often unintentionally practiced by those who skip breakfast and do not eat after an early dinner each day?
5.Larger portions in a shorter period of time
Some people may like this part a lot because you get to consume more food at once, leaving you feeling more full and satisfied, and you wouldn’t have to worry about eating later (because you probably wouldn’t even be hungry!). In a way, Intermittent Fasting can actually help prevent you from the typical binge on food at night after not eating all day at work, or the sooner-or-later binge-eating resulting from those calorie-restricted diets that are difficult to keep up with for life.
CONS of intermittent fasting:
1.Interference with the SOCIAL aspect of Eating
Eating is very much a social activity. When you think about it, all of our celebrations, milestones and life occasions revolve around food and the enjoyment of eating with the people we care about. Since this new style of eating is very different from the typical daily eating patterns of most people, it may interfere with your social hangouts which usually involve tons of food. This is because of the shortened time frame you have for eating and it can be difficult for you in social gatherings where everyone else is eating and sipping on beverages, making you awkwardly stand out from the crowd. Not to mention, you might be missing out on those late night romantic dinners, home-made family suppers, birthday dinners, lunch meetings with your boss and co-workers, and maybe even sharing a meal with your spouse and kids Not so fun.
We are all well-aware that life is unpredictable and can throw something at you out of the blue! So when changes to our agenda occur, we might get hungry and be much less productive, especially if you are used to eating lots of snacks or meals throughout the day, and all of sudden can’t. For those of us who are gym-goers, we might not even feel like we will have the energy or motivation to be active and do the things we actually like! Studies on breakfast consumption have shown positive outcomes such as promoting cognitive and academic performance as well as weight-loss maintenance in various individuals. Getting enough fuel throughout the day can help keep us in good spirits, energetic and productive.
3.Feasting = BINGE!
Since you only have a limited amount of time reserved for eating, some people may take the “Feasting” periods as an opportunity to eat more calories than they really need. When you’re hungry, or you anticipate a period of fasting coming up, it can be very tempting to go hog wild at the first sight of food. If the fasting element IN Intermittent Fasting were to create some sort of caloric deficit, it’s very possible that the feasting period easily undo it.
Some of us may experience digestion problems with these larger portioned-sized meals that we consume within a shorter amount of time. Larger volumes of food translates to more time needed to digest, which causes additional stress on your GI tract, leading to indigestion and bloating. This can have huge implications for those with IBS, who already have a more sensitive gut, inflammation of the GI, and disturbed bowel movements, and are therefore they are more susceptible to cramping, abdominal pain and bloating. Especially with IBS, you may already have difficulty obtaining all your nutritional requirements due to the uncomfortable symptoms that come along with it. That’s why people with digestive issues are recommended to eat at regular times, take time when eating, and not skip meals in order to have regular bowel functions.
So I know we just mentioned one particular study that showed greater lean muscle retention with Intermittent Fasting, but the reality is, the research here is mixed. Other studies have found no huge difference between continuous calorie restriction and fasting on parameters like weight loss, fat mass, fat-free mass, glucose homeostasis, cardioprotection, and reducing appetite. Clearly we need more research.
6.Unclear Impact on Heart
For cardiovascular markers such as total cholesterol, some mixed results were also observed in alternate-day intermittent fasting, in which both LDL (BAD cholesterol) and HDL (GOOD cholesterol) increased, while triglyceride levels decreased. However, other studies show that total cholesterol and LDL decreased (here, here) or HDL remained the same. Clearly we need more research here on Intermittent Fasting.
If you have a medical condition, it is the best to avoid this type of fasting because it may have the opposite effect on your health. For instance, those who are diabetic or hypoglycemic need glucose throughout the day and going without can have dangerous effects. If you are one of those people who feel nauseous or just don’t feel great going too long without eating, Intermittent Fasting is not suitable for you. It’s also important to put on the table that if you have ever had a history of an eating disorder – Intermittent Fasting is definitely not for you. Since Intermittent Fasting causes you to eat more food in a short amount of time, it may exacerbate potential disordered eating patterns such as a “binge-eating” mentality causing you to eat more food than your body can handle, or a “restrictive” mindset that is caught up with IF because of that desire to limit food-intake and become skinnier through restriction. This will definitely have adverse effects on your relationship with food and your body’s physical health.
If Intermittent Fasting is taken too seriously and excessively restricts energy and protein, there’s a real risk of nutrient deficiencies, electrolyte abnormalities, and issues with fertility and reproduction.
To expand more on the fertility issues, Intermittent Fasting is possibly linked to issues with menstruation, fertility, metabolism disruptions and early menopause in woman. According to animal studies, fasting led to decreases in body weight, blood glucose levels and more shockingly, reduced ovary size – significantly impacting fertility. In fact, this is because fasting interferes with hormone levels of LH (luteinizing hormone), estradiol and ghrelin, which may impact not only reproductive health, but appetite-regulation as well. Additionally, women typically eat less protein compared to men, and fasting women, even less. Low protein consumption means less amino acids that are needed to activate estrogen receptors and produce IGF-1 (Insulin-like Growth Factor) which is responsible for triggering the lining of the uterine wall to thicken and begin the reproductive cycle process. And if that wasn’t enough, since estrogen receptors are found throughout our bodies (such as our GI tract, bones and even brain), changed estrogen balance will change metabolic activity everywhere in your body as well (digestion, protein turnover, bone formation, recovery, growth, cognition and mood).
Although there aren’t any human studies on intermittent fasting’s effects on fertility, these significant results suggest that there may be similar effects on human females as well. So, if your reproductive health is at stake, your overall health is too as your hormones become out of whack, resulting in a decline in other body functions.
9.Potential Weight GAIN! (here, here)
Research on Intermittent Fasting’s effects on METABOLISM, has shown that there is decreased reliance on carbohydrates as the fuel source, as fatty acids are mainly used in its place. According to studies on short-term fasting, intermittent fasting protocols can cause glucose concentrations to decrease (reduced glucose oxidation) and lipolysis (fatty acid oxidation) to increase significantly during the first 24 hours. Therefore, IF can be beneficial as it promotes the breakdown of stored fat.
However, reducing energy intake too severely can lead to the body responding with physiological adaptations that can cause weight regain after losing the weight during fasting. This means that it is very likely that individuals will not maintain their weight loss after extreme restriction of food and in fact, can gain even more weight. Obviously, that’s not ideal.
Now to really get a BIGGER picture, let’s compare the research on the impact of spreading calories throughout the day vs. large meal binges to keep our bodies fueled throughout the day. If you are able to follow and stick to Intermittent Fasting, it can actually aid you in making successful changes in weight loss by reducing overall caloric intake from up to 20 to 25% over the course of a week (as long as you do not binge on your normal ad libitum days). Some studies have shown that Intermittent Fasting is an easy method of cutting calories if made a habit, but others may develop a habit of overeating as a result of fasting, which would result in increased body weight and issues involving insulin’s ability to regulate blood glucose which is strongly tied to weight maintenance.
Rather than overeating, Intermittent Fasting can make you have a slower metabolism as your body goes into starvation mode and begins to use your muscle protein as a source of fuel. Even a short 24 hour fast can lower your BMR (Basal Metabolic Rate), having negative health implications in the long-run!
For many of us, a better weight-loss approach may be eating several small meals throughout the day, which stabilizes our insulin levels and blood glucose, preventing any sort of ravenous meal gorging at the end of the day. It has been found that eating 6 times a day may even help maintain your lean muscle mass (which means faster metabolism!) compared to eating less frequently.
Now with all this info, the BIG QUESTION here is …
Should I start Intermittent Fasting?
Many potential health benefits have been observed from Intermittent fasting, but it is very important to remember that there are current limitations of intermittent fasting research and mixed results found in the different types of intermittent fasting. As of now, Intermittent fasting can be seen as an alternative to the traditional calorie restricted diet. In the end, you each person has their own way of eating and their own “diet personality,” which means that there is no one-size-fits-all, perfect diet that is suitable for everyone. What’s most important is that you assess your own eating habits and find out what approach works best for you.
Personally, I’m not convinced by the research and ultimately believe that any “diet” that requires you to disregard your body’s innate hunger and satiety cues is not likely to be sustained. But if you do decide to try Intermittent Fasting, always speak with a Registered Dietitian for personalized advice and supervision. Ultimately, the goal here is not to cause your body to go under any sort of chronic stress, but to nurture and show it some love by taking care of it, starting with a foundation of a nutritious diet.
Research by AK RD2B Rachel Shim