How effective is intermittent fasting for weight loss?

Hear the word “fasting” and most of us roll our eyes believing it to be another gimmicky diet.  But a new way of fasting for weight loss is becoming a very popular method being embraced by celebrities such as Jimmy Kimmel and Hugh Jackman among many others across the country.  This new weight loss approach is called intermittent fasting (IF) and may be one around for a while.   There is a growing body of research suggesting that cycling low-calorie days into your normal eating pattern may be good for not only losing weight but also our health. 

Kimmel credited his weight loss to IF and Jackman revealed he used IF to get in shape for his role in Wolverine in 2013. 

The questions to ask for the rest of us, is IF an effective, safe and scientifically approach to achieving a healthier body weight and can it help keep the weight off for good?

What is intermittent fasting?

Intermittent fasting is basically considered an occasional starvation but done in a strategic manner.  The idea is to cycle between periods of regular eating and fasting, during which you severely restrict your calorie intake.  Some people fast for hours, while some may go for a full day or longer. 

There are several different methods that can mean “intermittent fasting” but the most popular two are the “5:2 approach” or the “eight-hour approach.”  If using the 5:2 approach, this refers to limiting calorie intake – to about 500 calories a day - for two days a week.  The eight-hour approach is where you would only eat within an eight-hour window most days of the week – e.g., from 10 am to 6 pm. 

Enthusiasts of this diet hypothesize that these periods of fasting help to lower insulin levels, leading to metabolic advantages in that fatty acids will be released from adipose or fat stores using up fat for energy.  Since the fasting is intermittent, it should not cause your metabolism to decrease or slow down.  However, if a person were to fast for longer periods of time, then that could slow down the rate of calories burned. 

Pros of intermittent fasting

·      Eating less will result in weight loss – Because you are limiting the number of hours during the day of when you would be eating, you should lose weight.  Reducing calorie intake and only eating for a certain set number of hours a day means you are not “grazing” all day long and into the evening.  Comparing this to other fad diets that focus on increasing protein or fat but not necessarily reducing calories, intermittent fasting may be a better way for some people to lose weight.

·      You are not starving yourself – Many people equate “fasting” to mean to starve or drastically cut back on calories for days and days.  This is not the case with intermittent fasting.  It is more about cutting back on calories for short periods of time.  Doing so seems to affect your hunger and cravings over time.  As your body adjusts, you become satisfied more easily with smaller portions. If you are choosing healthy foods during the process, you also reduce your cravings for unhealthy foods, such as those loaded with refined sugars. 

·      Fasting may improve your overall health and extend your life – This is likely due to the ways that it affects cell and hormone function, according to several studies. In one recent study periodic fasting was linked to lower risks of heart disease, diabetes, cancer, and aging.

·      May improve blood lipid levels – Some studies on IF have shown it may decrease low-density lipoprotein (LDL) or “bad” cholesterol, as well as inflammation.  Additionally, IF may improve insulin resistance, which in turn, helps stabilize blood sugar levels. 

Cons of intermittent fasting

·      “Rebound effect” – Since you would be not eating as much or shortening the “window of time” you are eating during the day, you may compensate by eating more during your “window of eating opportunity.”  For instance, if your eating hours are between 10 am to 6 pm, you may make up for not eating breakfast by eating more at lunch. Or if you follow the 5:2 approach where you eat only 500 calories two days a week, you may overeat on the other days you are not fasting.  Therefore this “rebound effect” can wipe out any benefit of fasting, unless you are very careful about monitoring what you eat.

·      You may feel fatigued – Food is what gives us energy and when we cut back on calories or the window of time for eating, this can result in more fatigue and difficulty in concentrating during the day.  

·      Long term use is questionable – We are always searching for that one perfect method for weight loss that is relatively easy and doesn’t require us to give up the foods we love.  IF seems to fit this requirement.  But if we find ourselves very cranky and hungry on the days we are to eat only 500 calories or maybe we don’t want to eat only during certain hours of the day, sticking to a fasting diet may not be feasible or realistic long term.  You could probably do IF for a few weeks or even months, but for the rest of your life is unlikely.

In conclusion

There is no one-size-fits-all fasting diet.  The best and most effective diet plans are highly individualized.  While a fasting program such as IF may aid weight loss, it is not a plan that is practical or sustainable for everyone.

IF can be effective for some people for getting a jump start on weight loss, many of us can simply make smart lifestyle changes such as focusing on eating more vegetables and fruits, and choosing other health-promoting foods. 

Another consideration to keep in mind is that you may not know how your body will react physically and mentally to calorie restriction.  It generally is not recommended for anyone with diabetes as it could lead to problems with low blood sugar or hypoglycemia.  Even though fasting may seem easy, if you find yourself getting intense cravings during times when you are not supposed to be easy, you may end up eating all sorts of things you normally wouldn’t during the times you are allowed to eat. 

Overall, you have to consider how IF may affect you and for anyone with health issues, they should consult with their doctor if IF would be right for them.