There is much acclaim about the benefits of intermittent fasting (IF). It offers easy weight loss, immediate health improvements and "IF" the tests on animals are to be believed it can also increase our lifespan.
Is the hype true and is "IF" easy to follow?
IF eating plans follow many different programs alternating between eating and fasting. Popular plans are:-
The 5:2, is where you eat normally for 5 days and fast for 2 days. The fast day may be 25% of the "normal" day calorie intake and be around 500 to 600 calories/day.
The 8:16, is where you restrict your eating to an 8 hour window every 24 hours. For the remaining 16 hours you don't eat apart from up to a max of 40 calories.
The alternate day plan, one day normal eating followed by one day reducing your calorie intake by say 75%. Repeat the cycle.
There are many variations of the IF and they all claim similar benefits. Long term IF is an eating plan and not a diet.
Many people who follow IF, do not consciously restrict their calorie intake but still maintain a healthy weight. For people who are overweight, IF can be combined with some calorie restriction.
Is the hype true and is "IF" easy to follow?
IF eating plans follow many different programs alternating between eating and fasting. Popular plans are:-
The 5:2, is where you eat normally for 5 days and fast for 2 days. The fast day may be 25% of the "normal" day calorie intake and be around 500 to 600 calories/day.
The 8:16, is where you restrict your eating to an 8 hour window every 24 hours. For the remaining 16 hours you don't eat apart from up to a max of 40 calories.
The alternate day plan, one day normal eating followed by one day reducing your calorie intake by say 75%. Repeat the cycle.
There are many variations of the IF and they all claim similar benefits. Long term IF is an eating plan and not a diet.
Many people who follow IF, do not consciously restrict their calorie intake but still maintain a healthy weight. For people who are overweight, IF can be combined with some calorie restriction.
Some studies show increased fat loss and better muscle retention for those on a IF plan compared to dieters and where both groups follow the same calorie intake per day.
Some also appear to show similar weight loss amounts results between two IF groups, even when one group consumes more than the other. Presentation on intermittent fasting what is the evidence? , British Nutrition Foundation.
The IF theory
The IF theory
The theory of why IF works lies in our evolution and DNA, it is a compelling story.
In paleolithic times we had to hunt and forage for our food. The motivation to do this was hunger. Hunting and foraging took energy and required us to be strong and fit internally.
Our bodies therefore developed repair mechanisms so we were are in the best condition to survive. These repair mechanisms occur most when we start to feel hungry. Fasting triggers stem cell regeneration, University of Southern California.
In paleolithic times we had to hunt and forage for our food. The motivation to do this was hunger. Hunting and foraging took energy and required us to be strong and fit internally.
Our bodies therefore developed repair mechanisms so we were are in the best condition to survive. These repair mechanisms occur most when we start to feel hungry. Fasting triggers stem cell regeneration, University of Southern California.
When we eat it takes 6 to 8 hours for our bodies to use up the glycogen stores sufficiently, such that our bodies will start to burn fat for energy. To lose body fat we want to be in this zone for a longer time. The IF concept for fat loss.
The problem with eating every time we get hungry is that our glycogen and insulin levels are never reduced sufficiently for long enough to get the fat burning process going.
It seems that fat storage and burning is ongoing process and one that may be disrupted with modern day eating patterns, of eating as soon as we feel hungry. Where we only get the fat storage part of the equation working.
Will IF cause our bodies to metabolise protein and cause us to lose muscle mass?
Is it known that when we enter "starvation mode" our body will resort to burning protein as a fuel and consequently we will lose muscle mass. This in turn slows down our Basel Metabolic Rate (BMR) needing fewer calories to sustain our essential functions making us more susceptible to gaining fat.
This will not happen on the relatively short periods spent fasting on a IF plan. Particularly if we are eating sufficient amounts during the non fasting periods.
Muscle wastage for energy is known to occur with people on severe calorie restricted diets for a longer period of time. This was reported by an often quoted, study by Rockefeller University in the 1980s. It was reported that in people who restricted calories moderately their weight loss comprised 91% fat and 9% muscle, whereas people who severely restricted calories their weight loss comprised 48% fat and 42% muscle.
The article What happens to your metabolic processes when you stop feeding your body, on the Medical Daily website states that we would enter starvation mode after 72 hours.
So what is the best IF eating plan
Ultimately the optimum IF eating plan is the one that you can effectively incorporate into your schedule and that you are sufficiently comfortable with that it will become a habit.
The 5:2 fast diet plan promoted by Michael Mosley is a popular IF programme at, http://thefastdiet.co.uk/.
On this plan the cycle is 3 days where you eat normally for two days then fast for one. The fast day is actually 36 hours, where you consume 25% of the calories that would on normal days. For men the calorie intake is typically 2400 on normal days and 600 on fast days and respectively 2000 and 500 for woman.
For example, if you last eat on Monday evening you would not eat again until Wednesday morning. This seems quite tough and I am not sure how well you would sleep on Tuesday night. Michael Moseley acknowledge there are side effects and advise it may a couple of weeks to overcome these.
The other thing that puts me off this program is that on 3 day the days you fast change all the time. This is inevitably going to conflict with other regular activities if you are to maintain the 5:2.
Key point considers even if you reduce the 5:2 to a straight 24-hour fast and eat nothing at all until the 24 hours is finished, it seems like a rather unpleasant experience.
The 8:16 plan for men or 10:14 for women started by Martin Berkhan http://www.leangains.com/, seems easier to follow than the 5:2.
The 8:16 plan is something that I followed for 2 months earlier this year. This combined with exercising 4 times a week allowed me to lose 6kg from 81kg to 75kg and reduced my waist size measurement from 37 inches to 33 inches.
In terms of eating I didn't count calories, though I did check them now and again and found I was eating between 2000 to 2400 calories per day. I did cut back on carbs and limited my intake to 100g per day, sourced from fruit and vegetables and porridge. During those 2 months I stopped eating bread, potatoes and pasta.
The 8:16 plan isn’t hard to follow. I wouldn’t eat after 6:00PM until 9:00AM the next morning. What makes the 8:16 plan easy to follow is that much of the fasting is in the evening and overnight when and you’re either satiated or asleep. Also there is no problems going to sleep on an empty stomach such as on a 36 hour 5:2 IF.
The 8:16 plan is something that I followed for 2 months earlier this year. This combined with exercising 4 times a week allowed me to lose 6kg from 81kg to 75kg and reduced my waist size measurement from 37 inches to 33 inches.
In terms of eating I didn't count calories, though I did check them now and again and found I was eating between 2000 to 2400 calories per day. I did cut back on carbs and limited my intake to 100g per day, sourced from fruit and vegetables and porridge. During those 2 months I stopped eating bread, potatoes and pasta.
The 8:16 plan isn’t hard to follow. I wouldn’t eat after 6:00PM until 9:00AM the next morning. What makes the 8:16 plan easy to follow is that much of the fasting is in the evening and overnight when and you’re either satiated or asleep. Also there is no problems going to sleep on an empty stomach such as on a 36 hour 5:2 IF.
You will be hungry when you wake but this is quite motivational as you know it is working and it is only 2 or 3 hours until you can eat. This can also be a great time to exercise and burn some more fat.
On the program I went to to the gym in the evenings and I did find that on those evening I was starting to feel some small pangs when going to sleep, but not so much that it was a problem.
During those 2 months on the IF plan. I didn’t fast at the weekend for either one or both days. I also drank wine in "moderation" at the weekends.
The Every Other Day Diet is an alternate day IF plan by Kirsta Varady and Bill Gottlieb http://www.eoddiet.com/
This is a very simple IF with the only rule being only eat 500 calories every other day. The other days eat what you want and all foods are allowed.
The authors recommend that on the diet day you consume the 500 calories in one sitting, rather than divide it into smaller meals. This is what most people found easiest.
This IF plan is not one that excites me and I think similarly problematic to the 5:2. Also the recommendation that you can eat what you want on the alternate days does not seem a prudent way to reach good health. Taken as read this would include processed junk food which is poisoning our bodies.
Is Dr Varady just ignoring her professional knowledge just to make a cheap sale to the masses.
The 2-Day Diet by Michelle Harvie is a variant of 5:2 IF, http://www.thetwodaydiet.co.uk/
On the 2-Day Diet the diet days occur back to back one after the other. The rules for the diet days are that you cut back on carbs apart from vegetables, there is no calorie counting.
The plan provides recipes and guidelines about what you should eat and on the 2 days dieting your calorie intake may be around 1000/day. The creators of the 2-Day diet consider it a diet and not fasting.
The plan provides recipes and guidelines about what you should eat and on the 2 days dieting your calorie intake may be around 1000/day. The creators of the 2-Day diet consider it a diet and not fasting.
One benefit of a 2 day plan back to back is that it works on a 7 day cycle so you can plan to have your IF days on fixed days that suit your schedule.
This plan seems much more achievable than the 5:2 Fast Diet and easier to follow. Also unlike the Every Other Day Diet it does educate and encourage you on healthy eating.
The downside or question about the 2-day diet is whether you are getting the same metabolic benefits as you would on an IF plan. Apart from weight loss IF is also promoting hormones in the body repair and renew our cells.
Of course there is nothing stopping you adapting the 2-Day Diet with an IF schedule.
Key Point Summary
Both from personal experience and evidence researched to date it does seem that IF is effective in helping people lose weight and in turn this should reduce risks for metabolic syndrome, type 2 diabetes and heart disease.
In addition to the direct health benefits from losing weight there is also evidence fasting causes other changes in our body's chemistry that promote repair and regeneration of our cells. IF may be preventative against cancer.
There many IF programs available all following different routines and rules. Some also include exercise and dietary programs. So there definitely should be one that suits most individuals. The IF plan should be taken as a guide and the rules can be bent to suit your needs, ie if 8:16 is too much try 9:15 or 10:14, some benefit will be achieved.
To get the most from IF it needs to be undertaken with a healthy balanced diet, eat only whole and real foods. Eat junk and processed foods only on occasion. I have found that by eating whole foods that I cook from raw ingredients that my desire for junk food has disappeared, junk food just doesn't taste good by comparison.
We should be striving to change our eating habits from bad to good, in this way sustainable weight loss will be achieved..
Of the 4 IF plans presented above, I have followed the a 8:16 plan and found it works very well and was easy to follow. In fact my own brother has been following a 8:16 plan for a number of years and he works this into his busy schedule as a lawyer.
To address the question which IF is most effective requires consideration of the one allowing greatest body flat loss and can be comfortably followed such that it becomes a habit.
The 5:2 fast diet plan would certainly be effective in achieving weight loss, but can it be followed comfortably. I have my doubts.
The Every Other Day Diet, seems to combine alternate day severe calorie restriction with eat what you want and how you want the next day. On one hand I think trying to do alternate days at 500 calories will be tough. Then you are not helping your body the next day by potentially eating rubbish.
The food you eat does influence your body's hunger response. If you are eating high amounts of processed food with fructose the Ghrelin and Leptin hormone response will not work to stop you eating. See Sugar the Bitter Truth
The food you eat does influence your body's hunger response. If you are eating high amounts of processed food with fructose the Ghrelin and Leptin hormone response will not work to stop you eating. See Sugar the Bitter Truth
The 2-Day Diet is not an IF plan and may be too soft for rapid results. It also does not include a fasting period with only a restriction on carbs. So it is not known if the full IF benefits would be realized.
Overall I consider that Leangains 8:16 is the optimum for my needs and most easy for me to follow. This would be followed by an adapted 2-Day Diet, or to combine it with Leangains.
Overall I consider that Leangains 8:16 is the optimum for my needs and most easy for me to follow. This would be followed by an adapted 2-Day Diet, or to combine it with Leangains.
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