I’ve written before about the amazing scientifically proven benefits of intermittent fasting when combined with the keto diet, but what about intermittent fasting and weight loss results? Is this a way of reaching your weight loss goals easier and quicker even if you’re not on the keto diet?
Intermittent fasting for weight loss is most commonly done in one of these ways:
- The 16/8 method: This is the most popular, probably because it’s easy to follow and can be made to fit around social and work commitment. The simplest way to do this is to miss breakfast and have an 8-hour period of eating, which starts when you have lunch. You then wait 16 hours without eating before starting with lunch again. Not as tough as it sounds as the time you spend asleep counts towards your fasting time.
- Alternate day fast: This involves fasting for 24 hours, and eating normally on alternate days.
- The 5:2 diet: This is very popular right now. Slightly different from the other two methods. You consume 500–600 calories on two non-consecutive days of the week, but eat normally the other 5 days. More a fasting mimicking diet, than a true fast.
Obviously I’m a fan of combining keto and intermittent fasting, but for those of you who are not too sure about the low carb diet yet, I am going to set down the results that others have had from fasting combined with other diets, or just the fast without any changes to their diet at all.
Intermittent fasting is a short term intentional fast, and would not normally be for more than three days. It can be as short as 12 hours and we are all familiar with the fast overnight hence the first meal of the day is called breakfast – break/fast.
Intermittent fasting is not about reducing calories, although this often occurs as a side effect. On the days you can eat, you consume your normal amount of food.
It seems that intermittent fasting has been around for centuries, and is practiced in one form or the other by every major religion. Benjamin Franklin said way back in the 1700s that the best of all medicine was resting and fasting. So it would seem there really is nothing new under the sun.
So is intermittent fasting some sort of ancient wisdom? What happens to your body when you go on an intermittent fast?
When you stop eating your body begins to use its store of glycogen in the liver. This is a natural survival process and we power through our store of glycogen somewhere between 12 and 36 hours, depending upon our glycogen levels, our activity level and our metabolic rate.
Insulin levels drop which triggers the switch that enables your body to metabolize fat.
Once all the glycogen has been used up we enter a state of ketosis even if you are not on the keto diet. This is an important point to remember; once you have used up your store of glycogen you are using the same energy source as a person in ketosis because they are on the keto diet.
The keto diet can super charge the effects of intermittent fasting and a keto diet that is low in calories is a fast mimicking diet. In other words a low calorie low carbohydrate diet it is a way of intermittent fasting without actually having to go without all food. However, going low calorie for longer than a few days will have some unwanted effects.
So, is it worth going on the occasional fast while not dieting? How often would you need to do this? And to come back to our question: what are the weight loss results?
Intermittent fasting is not a calorie restricted diet, it’s a way of timing your meals to gain some benefits. You should eat normally at the times you are not fasting.
It has become widely accepted that it’s not what you eat, but when you eat that is important.
We’ve all heard the bro science about how missing a meal will drop our metabolic rate into our shoes, and cause us to double our body weight at our next meal. Thank goodness we now have some real science to tell us that is not true. It’s now known that the opposite is true: Intermittent fasting increases your metabolic rate.
This is in contrast to a calorie restricted diet which does cause a drop in metabolic rate.
Scientists studied a group of lean, healthy people over the course of an 84-hour fast. They discovered that their metabolic rate increased from as early as the first day and significantly increased again on day three.(1)
This means that on the days they could eat, they were less likely to gain weight.
These results confirm that if you do decide to use intermittent fasting as a weight loss strategy, you won’t have to worry about your metabolic rate.
There is an important distinction to make between intermittent fasting and actual starvation. Intermittent fasting is short term, and your body copes with this by using stored fat for energy.
When a fast goes on for too long the body enters a state of starvation. This is something completely different and as your body seeks to survive it will begin to use any source of energy available. This includes using protein from muscles as fuel. This is a dangerous state, and should not be used as a weight loss method.
Thankfully, science has found that intermittent fasting burned less muscle than a regular calorie restricted diet. (2). Although the subjects in each group lost similar amounts of fat, the fasting group retained more muscle mass.
Levels of Human Growth Hormone also quickly increase with intermittent fasting. This hormone helps with fat loss but also helps with muscle growth. (3)
There is good reason to intermittent fast and these short term fasts, with normal eating in between, will protect your muscle enabling you to lose fat weight only.
In response to the fact that you are not taking in nutrients your body will produce norepinephrine which is one of the chemicals involved in the flight or fight response to stress or danger. This chemical causes the fat cells to release fatty acids, to give you access to extra fuel in what it senses as an adverse environment. This process also accelerates weight loss.
The biggest reason intermittent fasting causes weight loss is that most people end up eating few calories overall even when they eat normally or slightly more on their eating days.
One study found that on average people lost 0.35kg/ 0.55 lb each week with intermittent fasting, and 0.75kg/1.65lb when they fasted for alternate days (4)
Importantly, these people were losing dangerous belly fat.
So does the evidence stack up for the use of intermittent fasting for weight loss?
In three small words, yes it does.
Intermittent fasting can be a very effective way of loosing weight without suffering the drop in metabolic rate which can be a side effect of a continual calorie deficit.
In fact, intermittent fasting increases your metabolism, along with preserving your important muscle mass.
Further, the practice of intermittent fasting is easy to follow and you can enjoy your normal foods on the days you can eat. You can organize your fasting/eating schedule to fit around work and your social life.
This will make dieting for weight loss easier to follow. It also allows for good quality nutritious foods to be eaten at the times you’ve set aside for meals.
There is overwhelming evidence that this approach to weight loss is healthier than calorie restriction, and has several other benefits too.
One of the major benefits of intermittent fasting is autophagy. Even if your focus is on just weight loss, autophagy and it’s amazing health benefits are worth your time to consider.
You can read more about this here
You do need to make sure that you’re eating enough, even if you are finding that you don’t feel hungry on your food days. On the other hand, if you think intermittent fasting means its OK to have burgers and fries on your days off, then you are more than likely to see that your weight loss stalls.
Not only is fast food/processed food not good for your health, it is almost always very calorie dense and so you would be undoing a lot of the good that could come your way with intermittent fasting.
If you do feel like eating a bit more than normal at meal times, this is probably going to be OK. However, your aim should be to eat a healthy balanced meal, there is no need to try to compensate for your fasting days.
Intermittent fasting isn’t for everyone, and not everyone should consider this as a weight loss strategy.
You can read more about intermittent fasting here
This could be a simple and flexible way for you to reach your weight loss goals. The best diet for you is always going to be one that you’re going to stay with for long enough to be able to reach your weight goals.
1. Resting energy expenditure in short-term starvation is increased as a result of an increase in serum norepinephrine.
Zauner C1, Schneeweiss B, Kranz A, Madl C, Ratheiser K, Kramer L, Roth E, Schneider B, Lenz K.
2. Intermittent versus daily calorie restriction: which diet regimen is more effective for weight loss?