 Intermittent Fasting has become a popular diet concept for fat loss in the last few years; many swear by it, and many swear it will cause potential long-term problems. Will you be able to reap a multitude of benefits from it? Or will it ultimately cause you to gain fat, lose muscle and put you on the brink of eating disorders? Read about the basics you need to know: the great ways it can help you lose weight, the potential ways it might backfire, and my personal experience with Intermittent Fasting (what worked, what didn't). *All nutritional and fitness info must be discussed with your doctor before any changes to diet or exercise regime are implemented The Concept Intermittent Fasting (IF) is not so much a diet, as a diet pattern; it is essentially increasing the amount of time you are fasting (not eating) and decreasing the amount of time you are feasting (eating). If your typical day consists of breakfast at 7am, lunch at noon, dinner at 6pm, and ends with snacks at 8 or 9pm then you are eating for 16hrs and fasting for 8hrs. IF essentially reverses this so you will fast for 16+hrs and eat for 8hrs (or less). The longer you can increase the fasting time the greater the potential benefits, so this is up to the individual; in general, the protocol would be 16/8 (fast/feast), 18/6 or 20/4. You might even make it up to 24hrs fasting, meaning if you finish eating at 4pm day 1, you would then fast until 4pm the next day and eat 1 or 2 meals that day until 6 or 8pm. So why would you do this? Potential Benefits: Fat burning As we go throughout the day – and night – the body goes through a cycle of fed vs fasted states. During feasting the body breaks food down into glucose which is then used for fuel; once the glucose is depleted the body needs to look around for another fuel source, ie. our stored fat. This process takes several hours; how long depends on the type and quantity of food we have eaten - among other factors - but in general we reach the fully fasted fat burning state after 12hrs. Once we reach the fasted state our body will start sending us signals to eat again, ie hunger; eating again will signal to our body will stop using our stored fat as fuel and switch back to using the glucose from food. By extending the number of hours we are in a fasted state, we are essentially prolonging the time our body will keep using our stored fat as fuel. Insulin sensitivity As we eat, food gets broken down into glucose, and once the glucose hits our bloodstream our blood sugar level rises. This level must be brought down to a neutral level otherwise our body will remain in a hyperglycemic state. The body then works to lower our blood-sugar levels by releasing insulin from the pancreas. Insulin acts as a broom which runs through our blood, sweeping everything from our bloodstream into our cells - proteins, fats, and glucose – and signals to the body that it is in “fat storing mode” not “fat burning mode”. How much insulin is produced is dependant upon several factors, including what we eat. Foods high in sugar, as well as processed and refined foods cause a much greater spike in blood sugar and therefore prompt more insulin to be released, vs whole grains, proteins and healthy fats (read more: Insulin: Friend or Foe?). The other factor determining how much insulin is released by the pancreas is how insulin responsive or sensitive we are. The body is adaptive, and insulin is much like caffeine; often the more caffeine we ingest the more we need to ingest in order to feel the effects, our body has adapted and become resistant to the effects of caffeine. In much the same way our body can become resistant to insulin; the pancreas needs to create more and more insulin in order to lower our blood sugar levels back to normal. This creates a state of Insulin Resistance, where insulin is in near constant production, constantly signalling our body to stop burning fat and store it instead. If we keep our body in a constant “fed” state, not only will it continue to produce insulin and store fat, but it will also “lose the habit” of switching over to using stored fat as fuel, and instead continue to demand glucose for energy (by sending hunger signals). Intermittent Fasting helps train our body to switch back to using stored fat as energy when glucose is not available. When this happens we have become “fat adapted”. By having our body “practice” becoming fat adapted we also train our body to become more insulin sensitive; over time the pancreas will start producing less insulin in response to the food we eat which means that less food will be stored as fat. Studies with Type II Diabetics have in fact shown short term IF effective to help lower fasting blood glucose levels. Metabolic Flexibility = Diet Flexibility The ability to switch back and forth from using glucose and fat as fuel sources makes us metabolically flexible. This metabolic flexibility actually allows you to be more flexible in your diet due to insulin sensitivity, and studies show that fasted exercise increases metabolic flexibility and insulin sensitivity. Once you have reached a state where you are easily able to switch back and forth from using available fuel sources (glucose/fat) without hunger, light headedness or nausea you are likely insulin sensitive, meaning that your body will have less of an insulin response to a high carb meal. This equates to diet flexibility with less fat storage caused by an occasional high carb cheat meal/social event/holiday celebration etc. Of course, abusing this will put you back in a state of insulin resistance so use this flexibility wisely! Calorie deficit The idea of IF is that you still eat all your calories for the day, just in a shorter period of time. However, if your goal is weight loss, your allotted calories for the day will keep you in a calorie deficit (read more about calorie deficit to achieve weight loss) and this can be difficult to stick to. By decreasing the amount of hours you are eating you will essentially be skipping a meal, and this can make it easier to stick to a calorie deficit. Due to the increase in fat burning while fasting some people find it possible to lose body fat without reducing their caloric intake below maintenance (no deficit but no additional calories). Reduced hunger As our body becomes fat adapted it gets better at transitioning to using fat as fuel instead of crying out for more glucose by making us hungry. You should notice reduced hunger during the fasting period enabling you to stay in the fasted state for longer and longer. This study actually showed a that there was no increase in ghrelin (read more about our hunger hormone) while fasting, despite not eating for up to 84hrs. More satiating meals As all your food will be eaten within a few hours many people find this more satisfying than having them spread out throughout the day. The same number of calories in 12-16hrs will mean less food per meal and can often leave us un-satiated after a meal. Ease of diet protocol The great thing about IF is how flexible it is, any amount of fasting past 12hrs can help with fat burning. Start slow and increase fasting hours to a level that suits you, or use a protocol that alternates fasting and non-fasting days (see more details below). You can either work social events into a feasting period, or take a day off from IF while still gaining benefits throughout the week. Fast for 18hrs one day and 13hrs for the next day, both days you will benefit. Of course, the more consistent you are with your fasting strategy the more adapted to that strategy you will become making it easier to get through the fasting period. Mindful Eating As the goal is to stay fasted for a certain number of hours, you need to be mindful of what you eat; casual grazing will put an end to your fast and put you back into a state of using glucose instead of fat for fuel. This can be beneficial to help stay in a calorie deficit (or maintenance); sometimes those grazing calories are what put us over the top of our desired calorie range for the day. No more "just a nibble of cheese before bed" or "just half of one of the donuts left in the breakroom for breakfast". Potential drawbacks: Hunger during fasting No matter what protocol you follow you are highly likely to experience some hunger, at least at the beginning. Many people start with IF only to abandon it a few days (or hours) later, however starting slowly and increasing fasting time gradually can help. If you usually eat breakfast at 7am, push it back an hour each day until you are so close to lunch you can just skip breakfast altogether. Make sure to not snack after dinner so you can begin the fasting window as soon as you finish dinner. Undereating Eating meals larger than you are used to might be a struggle for some people, especially if your caloric needs are high. If you need to eat 2,500 (or more) calories in a 4hr window you might need to include some calorie dense foods in order to lower the food volume. These are generally foods high in fat, which makes it ideal for a ketogenic diet, but not if you are following a moderate carb, moderate protein, low fat diet. This could lead to eating less calories than you need, causing muscle loss, decreased energy, and increased potential for health issues. Over eating and binge eating For some people the opposite might be true; once they stop fasting and start eating they find it difficult to stop. Binge eating is defined as “episodes of uncontrolled eating”, often past the point of feeling uncomfortably full. For some, the mentality of fast-or-feast can mean taking the feast portion over the top, binge eating way past their allotted calories. Many psychologists caution against IF due to the risk of binge eating and you can find many personal accounts online of people claiming IF caused binge eating behaviour for them, either while doing IF, or after returning to a normal pattern of eating. Eating all your calories in 1-3 meals can mean quite a lot of food at each sitting and can definitely leave you feeling very full; after returning to a regular pattern of eating (spread out over 12+ hours) means you will not feel as full after each meal. For some people this is difficult and they are hungry unless they feel stuffed at each meal, leading to overeating all day long and of course weight gain. There have also been several studies showing that people doing an alternate fast/feast day ended up over eating on their feast days by the same number of calories as they saved on the fast day, making it a wash for their weekly caloric intake. Not to mention all the studies done on how eating breakfast, particularly one high in protein (ie. eggs) can help you control cravings and eat less throughout the day, leading to weight loss. A lot of the studies are done on overweight women (like this one with adolescent girls), however the sheer volume of studies showing this result speaks volumes. Eating junk IF only dictates how you eat, not what you eat; if before IF you were eating low quality food, IF will not inherently change this. For some, IF might give them to motivation to make better choices, however some people need more guidance, and others still use IF an “excuse” to continue to eat junk. This might actually lead to weight loss at the beginning (eating junk for 6hrs is better than eating it for 12hrs!), however it will not create better eating habits or an improved health profile. Muscle loss? Any time you are in a diet that puts you in a calorie deficit it is inevitable that you will lose some muscle mass along with the fat loss. Whether this will happen more or less while doing IF is much debated. Some studies show a slight loss of lean body mass (LBM) during short term IF, while others show no loss of LBM. Most of the studies are done on overweight individuals, are short term, with small test groups, so to be able to definitively say yes, or no, more research is needed. Human Growth Hormone (HGH) is a hormone released by the pituitary glad while we sleep, during exercise and during fasting; it helps to regulate body composition, body fluids, muscle and bone growth, sugar and fat metabolism, and possibly heart function. This study shows that fasting can increase HGH, however this was done on a 5 day fast, 1 day feast protocol which is not advisable, or even possible for most people. And while many claim the increase in HGH achieved after fasting for a shorter period (24hrs) actually help them gain muscle mass, many claim that the increase in HGH is not great enough to offset the muscle loss during fasting and calorie restriction. Some studies even suggest that high levels of HGH can lead to insulin resistance which could lead to fat storage. Training fasted is often a component of IF, especially if you train first thing in the morning, and while this can be great for fat loss, it can also lead to loss of muscle (read more about Fasted Training). The ingestion of BCAAs (read more about BCAAs) can help mitigate this potential loss of muscle mass, but the question of whether you are still fasted while ingesting BCAAs is much debated. One of the popular IF protocols, Lean Gains, recommends the use of BCAAs while training fasting, while others say that BCAAs will break your fast. Hormones While more studies are needed, it is sure that IF can make changes to your hormones. Some of these changes can be potentially positive, such as improved insulin sensitivity, increased HGH, increased Leptin sensitivity (our satiety hormone), and no negative changes to ghrelin (our hunger hormone). However some changes can be detrimental: fasting can increase cortisol (our stress hormone, read more) as well as decrease estrogen and testosterone (bad for fertility, muscle building and fat loss, although some might benefit from decreased estrogen - both men and women - read more about Estrogen Dominance). For some, these changes in hormones can lead to weight gain and other health issues; talking to your doctor first and potentially checking hormone levels is recommended. Medications If you are taking any medications then you should definitely discuss IF with your doctor to make sure there will be no complications from changing your diet pattern. Different protocols If you decide you would like to try IF, start by deciding if there is a specific protocol you would like to try. There are a few methods that have been popular for several years and offer a lot of resources; following one of them specifically could help you through any rough patches: Lean Gains Popularized by Martin Berkhan, Lean Gains is a 16/8 is a style of IF, where the fasting period is 16 hours, and the feeding window is 8 hours. During the 8 hours you may eat as few or as many meals as you like, with the most frequent iteration being three meals. Designed specifically with training in mind, Lean Gains includes specific post-workout suggestions and recommendations, including using BCAAs around training (although they recommend a lot of BCAAs, more than the average person would take). The Warrier Diet The Warrior Diet is a 20 hour fast followed by a 4 hour feeding period; as the name implies this is inspired by the nutritional habits of the warriors who weren’t in the habit of eating six meals per day. The diet is technically not IF, as during the fasting part of the day you are allowed to eat a few servings of raw fruits and vegetables, and a few servings of protein (protein shakes included) if needed/wanted. This amounts essentially to snacking during the day and skipping all meals until you have one large meal at the end of the day. Eat Stop Eat Eat Stop Eat is a 24hr fasting period, done 1-3 times a week (most often 2 times); this means that if your last meal of was at 7pm you would fast until 7pm the next day and then enjoy one large meal. The idea is that this way you do not feel deprived as this one meal will be high calorie and satisfying. Tips to make IF easier:
Takeaway Ultimately, the most important factor in order to lose weight is calorie restriction. Calorie deficit has been shown time and time again to beat any other weight loss method, including Intermittent Fasting.
My experience with IF As I began writing this article I decided to dabble with some intermittent fasting. I say dabble as this was by no means a scientific exploration, simply a "try a few things and see how I feel" approach. I had tried IF a few years ago – albeit half-heartedly – got too hungry and gave up, but this time it seemed easier. I started one day after I had finished training; as I am one of those people for whom exercise suppresses my appetite both during and a short while after training I figured this would be a good place to start "experimenting". I had ingested some protein pre-workout around 6am, trained from 7:30-9:30am, then ate my first meal around 2pm. Not bad for my first day but as I had broken my fast with protein at 6am, not technically a long enough fast to count as IF. I knew I had to cut my pre workout protein and train fasted, which I did. This meant that I stopped eating around 6:15-6:30pm, and then didn't eat until 12:00 the next day, an almost 18hr fast, 6hr feast. What I liked:
What I didn't like:
My results:
My takeaway: I have settled into a hybrid version of IF, keeping the things I liked and removing the things I didn't:
*All nutritional and fitness info must be discussed with your doctor before any changes to diet or exercise regime are implemented. Change nothing and nothing will change; without change, there can be no progress! Related Articles:
They Ketogenic Diet: The Concept, Benefits and Drawbacks Pre and Post Workout Nutrition: Maximize Your Training Gains with Correct Nutrition Your Metabolism: Can You Change It? Insulin: Friend or Foe? Nutrition 101: Master the Basics Fasted Cardio: Yes it Can Help You Shed Some Body Fat, but is There a Better Way? BCAAs: What are They, and What Can They do for You? Metabolic Conditioning: Why You Should do This Instead of Cardio 3/1/2018 03:46:42 am
Thanks. This article is useful and very inspiring.
Fitness Progression
3/1/2018 10:41:48 am
Thanks for the info, always good to have a resource that we can use (with our doctor's approval). Comments are closed.
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