By Dr Joe
Can you lose weight with intermittent fasting? Okay, hold on a minute, this question is like asking me this: can you lose weight without eating. Do you agree both questions are similar?
Food is what provides you with your energy needs. Food is what keeps you alive and kicking. In the same vein, food is what makes you gain weight. Yes, there may be other factors involved in weight gain like being on certain medication, not being physically active etc, but at the very core of weight gain lies your food intake.
Your food intake is the equivalence of your energy intake. So, if you deprive yourself of that energy intake, something has got to give. What’s that? Well, simple, you will have to draw on your energy stores – your fat.
Fat in your body is your ‘Savings Bank Account’. What happens when you run out of money in your ‘Current Account or Checking Account’, you tap into your savings, right?
Same thing happens when you do intermittent fasting. Not eating when you are fasting means you are going run out of “money” soon in your current or checking account. Your ‘Current or Checking Account‘ is your Glycogen stores. Glycogen stores are your go-to everyday spend money.
When you exhaust your glycogen stores when you don’t eat, you will have to draw on the “money” in your savings pretty soon – the FAT bank.
Because even if you lie there and do nothing at all, your body still needs energy to perform basic functions like breathing, talking, texting, your heart beating, thinking, reading that book or watching that television. All of those activities that happen spontaneously to keep you alive require energy. In fact, your body needs energy to burn energy i.e the metabolic process needs energy to power on.
That energy need constitutes the basal metabolic rate which has to come from somewhere if you are not eating – Your fat stores.
Simple answer to the question of whether you can lose weight on intermittent fasting is; Yes, you can lose weight with intermittent fasting, emphatically.
I will go as far as saying, you can lose weight without dieting. Why do I say you can lose weight without dieting? Well, you can, using intermittent fasting.
Because strictly speaking, intermittent fasting is not a diet. Intermittent fasting is a weight loss tool NOT a diet. So, by doing fasting like the 16/8 intermittent fasting, you can lose weight without dieting. Can I repeat that. Intermittent fasting is NOT a diet.
If you think about it there is an element of calorie restriction with intermittent fasting and calorie restriction inevitably leads to weight loss, right?
If you are depriving yourself of calories for any extended periods, such that your body doesn’t over-commit, then it stands to reason that you should lose weight.
Can you lose weight with intermittent fasting – The Science
This review looked at a lot of studies and reached the conclusion that intermittent fasting or alternate day fasting is an option for achieving weight loss and weight maintenance.
This study looked at 240 participants who were on the Ramadan fast. They found significant reductions in both weight and BMI during the fasting period. For some reason the men in the study had more reductions than the women. Maybe the women needed longer time to match the weight reduction seen in the men.
Another study examined what kind of weight could be lost with alternate day fasting over a 12-week period. In it the average weight lost by the subjects in the study was 11 and a half lbs in addition to a fat mass reduction of 7 lbs. They concluded that alternate day fasting was an effective method for weight loss.
If you really want to explore the potential of weight loss, then you may want to know what effect intermittent fasting has on glucose metabolism. In all my research, one thing that was consistent with practically every study was that fasting had a consistent capability to reduce fasting blood glucose and fasting blood insulin levels.
What does this mean?
Put simply anything that helps your body deal with insulin load and makes your body cells more insulin sensitive is a joy to behold.
High blood insulin levels encourage weight gain through fat preservation. Lower blood glucose levels on the other hand prevents prediabetes and type 2 diabetes.
This study of healthy Ramadan fasting Male volunteers recruited to see the effect of fasting on glucose, insulin resistance, adiponectin (a protein that’s involved in the development of insulin resistance) as well as insulin resistance. These parameters were measured just before the fast began and 4 weeks later into the fast. See arrows in diagram below.
Key to graph above
A = Blood Glucose
B = Fasting Plasma Insulin
C = Insulin Sensitivity
D = Insulin Resistance
In the one month of Ramadan Fasting, it wasn’t surprising that the participants in the study dropped their body weight. In response to their weight loss, their adiponectin levels dropped and there was a correlation with the amount of weight lost.
More importantly, there was a consistent increase in insulin sensitivity and a reduction in insulin resistance as plasma insulin and blood glucose levels were lowered on account of the fast. The conclusion from that study being that intermittent fasting has a positive impact on metabolism.
The video below explains more…
How much weight can you lose on intermittent fasting?
Naturally how much weight can be lost on intermittent fasting would vary from person to person as well as your personal discipline. The key here is to be careful with your meals in your feeding days. The last thing you want to do when you are doing intermittent fasting is to over-compensate or over-indulge in the days you are not fasting.
Just eat sensibly and avoid processed foods too, because foods that are overly processed will have refined sugars and trans-fat all of which are unhealthy.
More importantly, refined, heavily processed foods tend to spike insulin. Remember, one objective of intermittent fasting is that, you drive down insulin levels to draw on your fat stores.
As expected how much weight was lost on intermittent fasting also varied in the research studies. I have already mentioned this study earlier. In it the participants lost an average of 11 lbs and a half of weight over the 12-week period of the intermittent fasting.
This meta-analysis of different weight loss on intermittent fasting studies also revealed that participants can expect to lose 3 – 7% of body weight during fasts lasting between 3 – 12 weeks.
Those are figures extracted from research studies, but of course you could lose more or less weight compared to those individuals who have been studied. The other thing to realize is those studies only ran for a small duration and they do not include exercise or any workout whatsoever.
If you add a workout routine to your intermittent fasting, heaven knows how much weight you will shed. I expect the weight loss to be exponential.
How much fat does intermittent fasting burn?
Just like overall weight loss, the amount of fat loss on intermittent fasting will vary between individuals. Factors such as age and sex have been known to play some role in terms of how much fat one could lose when you undertake intermittent fasting.
A study on Ramadan fasting showed a fat loss of between 2.3% – 4.3% over 20 days of Ramadan fasting. In that study waist and hip circumferences fell in most subjects, except females aged 36-70 years. You could argue in that study the measurements were taken only after 20 days and more encouraging results would be had in the women if the study was more prolonged.
This study from the Human Nutrition Research Unit (HNRU) at the University of Illinois, Chicago looked at the effect of alternate day fasting on a variety of parameters one of which was how much fat can you lose on intermittent fasting.
They recruited subjects aged 35–65 years; BMI between 30 and 39.9 kg/m2; weight stable for 3 months prior to the beginning of the study. They found that alternate day fasting after a period of 8 weeks reduced fat by nearly 12 lbs in the participants.
Another study looked at the rate at which we burn fat on intermittent fasting. In this study the alternate day fasting model was also employed. What was found in the study was a swinging pattern in the way fat was burnt or oxidized. On the days the subjects in the study ate, fat oxidation slowed down and similarly on fasting days, fat burning accelerated. Overall fat oxidation was increased by an average of ≥15 g/day on fasting days.
This study gives a very good window to what is happening in our body. When you intermittently fast, you raid your fat stores because there’s no fresh supply of calories. Not only are you raiding your fat stores during intermittent fasting, your rate of fat burning actually goes up which translates to a more efficient way of fat loss.
It’s clear that if you don’t eat, you are giving your body a break. Not only that you are going to exhaust your glycogen stores very quickly. Do you know how long it takes for your body to use up its glycogen stores? 8 – 10 hours, that’s how long.
Yes, withing 10 hours, certainly by 12 hours, you would have exhausted your glycogen stores. What does your body do next? It turns to the fat stores because intermittent fasting drives down insulin levels.
And insulin is what holds the key to the fat stores. Once insulin levels have been driven low, your fat stores become accessible preserving your body’s resting metabolic rate.
That’s the beauty of intermittent fasting. The weight loss or should I say, fat loss associated with intermittent fasting is better than you will see with dieting or exercise.
So, if you are thinking of weight loss without dieting or weight loss without exercise, intermittent fasting is your best bet.
And you know what, intermittent fasting is free. You only need to learn to do it properly and you are on your way.
Suggested further reading:
How to Avoid Complicated Diet Rules and Prevent Rebound Weight GAIN
Dr. Joe