Intermittent Fasting vs Calorie Restriction Statistics & Facts

Don’t you just love the quick fix… you know, do something for 3 days and presto you are rich, or you are thin, or you are in love! Yeah, wouldn’t it be nice if those things actually worked… too bad they don’t. That’s our topic today, what’s the best way to lose weight. Is it through a plan of intermittent fasting or is it the “crash diet” in which you restrict your calories very low in order to lose weight quickly?  

The typical “crash diet” or “fad diet” can range wildly however the basic premise that we can all agree on is that they are supposed to offer a VERY quick result. As in, you are heading to the beach in 2 weeks… and you need to lose 30-pounds. Or you are getting married next month and need to drop 15-pounds to fit into that dress. We know the term and we all know what it means but why don’t they work – what is the science backing up the problem.

The American Academy of Family Physicians (AAFP) state that using a detox, or an extreme limiting of calories might show a drop on the scales, but that weight is often water weight and lean muscle being lost. You might see the scale drop, but the mirror will not reflect a visible change and once you start eating again or eating normal again, you’ll not only rebound to the original weight but typically pick up more weight.  

Dr. Noble of the AAFP says that cleanses and fad diets offer little more than a very temporary drop on the scale however these diet fads will not help you to burn extra calories and that is what’s required to help drop weight that you can see on the scale and in the mirror.

Calorie Restriction Research Studies

In a recent study people who ate a very low-calorie diet of 500 calories per day for five weeks lost a similar amount of weight as those that ate 1,250 calories per day for 12-weeks. However, the very low or starvation dieters lost more lean muscle mass and even 30 days after the diet was over still had less muscle mass than the other group. Muscle mass is what raises your resting metabolism, and this is key in losing weight over the long term and keeping it off. Your resting metabolic rate is how many calories you burn at rest, i.e. not working out… so you can guess if your burning more calories at rest you’ll be able to burn more fat each and every day. 

Christopher Mohr, Ph.D., RD says that a typical 200-pound male wanting to lose weight should drop his caloric intake no lower than 1,800 calories per day in order to safely lose weight. This represents about a 25% reduction from that male’s normal calorie intake. We now have some framework for our question; we know that we can’t just drop our calories to 500 each day and expect that to work. What about adjusting down 25% like Dr. Mohr suggests or could intermittent fasting offer us a boost to reaching our swimsuit season goals. 

How does Intermittent Fasting Work?

Intermittent fasting works simply because we are eating fewer calories over the week; we are on the right track here – fewer calories is a good thing. While in the fasting state you are basically not eating anything, zero calories. Then you break this fasted time with regular meals again so in theory this should work. Unless – unless, you gorge yourself with so many extra calories during your feeding time that you are still eating the same or maybe even more calories over a weeks’ time frame. We can see here that we have all the ingredients for a wonderful scientific study on what would happen if 2 groups went head to head in a weight loss battle. One group using intermittent fasting while the other group restricted their calories by the 25% recommended. Hey, good thing for us there was a study done that just published its findings in May of this year, 2020… how’s that for perfect timing! 

Fasting Statistics

A study posted in the Journal of American Medical Association this May was hunting the facts for this very question. Here is what they discovered: 

They used two popular methods of dieting: 

  1. Alternate-day fasting, where the subjects would fast for 24-hours at a time using 25% of their typical caloric intake on the fasting time. Then during the feeding time frame of 24-hours they would eat 125% of their daily caloric intake needs. 
  2. The typical American style of dieting, this is the one we’ve all tried before and think of when someone says they are heading to the beach next month and need a diet. The subjects here aimed to eat slightly less than their daily caloric needs; reducing the calories by 25%. So, if a subject needed 2,500 calories to support their body daily, they would reduce by 25% and eat only 1,875 calories that day. 

The study lasted a full year divided into two 6-month sections. The first 6-months were built to lose weight and then the last 6-months were geared toward the weight maintenance phase. They choose one hundred people in total for the study, 86 women and 14 men with a wide age range. The mean age was 44 years old however there were participants from 18 to 64. They were all classified as obese, but they didn’t have a metabolic disease like diabetes or metabolic syndrome. They also made sure their blood pressure and cholesterol were all within a normal range; simply put, they all needed to lose weight but were healthy adults besides that. They grouped the subjects into 3 sections – the first was given the alternate-day fasting plan, the second took part in the calorie restriction diet and the third group would act as the control and change nothing in their day to day routines. The subjects would be tracked via an MRI scanner to determine total body fat and weight. 

Give us the results already… enough with the back story! Ok, get ready for shocker… 

Both groups lost about the same amount of weight – yup, same results! The alternate-day fasting group lost about 6% of their body fat while the calorie restrictors lost 5.3% of their body fat. Also, not surprising the drop-out rate of the alternate-day fasting subject was much higher than the calorie restriction group. 13 of the 34 alternate-day fasters dropped out of the study while only 10 of the 35 dropped from the calorie restriction group.

However, even those results aren’t stunning… only 3 extra people dropped out on the fasting program – hardly a decisive victory. The fasting group also saw more people blowing their calorie goals, meaning that when they were eating, they were eating more than the 125% of the calories that the program allowed. The only true shocking result that the medical group still couldn’t account for is that the alternate-day intermittent fasting subjects saw an increase in their LDL levels (this is what we consider to be “bad” cholesterol) while the calorie restriction group saw no increase whatsoever. 

When a study like this is spilt right down the middle it can be hard to find some good takeaways, that you can put into practice in your life. I think one important thing to remember is that while no clear winner is shown, the bonus is that both ways worked equally well so you can really choose whatever works best for you. Remember that the best diet in the world is the one that you can stick to and turn into a way of life. Ditch the fad diets, the crash diets and the starvation methods you used back in college to prep for spring break ’95 – you’re an adult now and it’s time to start dieting as such. Pick a plan that you can stick to, pick a plan that’s healthy and make this plan a way of life – you’ll be healthier, you’ll live longer and bonus you’ll look even better in that swimsuit than you did back in college!