Lose/lose? The real scoop on intermittent dieting vs. traditional dieting

Diets are terrible. Almost everyone tries one, and almost everyone fails at it. Perhaps because diets are hard to stick with. After a few months or a few weeks, people fall back into old habits.

That's why intermittent fasting is so appealing. The idea is simple: you only have to diet some of the time.

There are many different versions of intermittent fasting out there. One of the most popular was the 5:2 diet which became popular in the UK before moving to North America. It was featured on the BBC show Horizon and quickly became wildly popular. The 5:2 diet says that you can eat whatever you want for 5 days of the week and only have to cut back for the other two. Although it's called a "fasting" diet, in reality people are just cutting back rather than not eating during those 2 days. On the fasting days you are supposed to eat just 500 calories (a quarter of the normal daily amount of calories) or just one meal for that day. If you get hungry around dinnertime, grin and bear it until tomorrow when you can have bacon and eggs for breakfast.

If two days a week is too easy for you, a new version of intermittent fasting has started popping up. Alternate day fasting, as the name implies, is a one-on/one-off schedule where you eat very little one day, and then eat to your heart's content on the next.

The theory is that most people can stick with the self-denial of dieting for 24 hours if they know that their cheat day is just over the horizon. It also assumes, rightly or wrongly, that people are not going to go crazy on the non-fasting days and undo whatever good they did the day before.

It makes sense on a theoretical level, but the real question is, does it work?

A recent study published in JAMA Internal Medicine at least partly answers that question. Researchers took 100 obese adults and divided them into 3 groups. The first group was told to continue their regular habits. The second intermittent fasting group ate a single 500-calorie meal on "fasting" days while on "feasting" days they could eat up to 25% more than they usually did. The third group was told to follow a conventional diet where they simply ate less every day.

The results were a surprise to the researchers because intermittent fasting did not outperform its conventional counterpart. There was no difference between intermittent fasting and conventional diets. Both groups did equally well. Or, if you are a nihilist, both groups did equally poorly. At six months, both groups had lost just under 7 pounds. By one year, the number had slipped back to about 6 pounds.

In terms of weight loss, body fat, blood pressure, blood sugar, insulin levels and inflammatory markers, there was no difference between intermittent fast and simply eating a little less on a daily basis. In fact the intermittent fasting group had slightly higher cholesterol levels at one year, although the difference was minimal and probably not significant in terms of impacting your health.

In fact, intermittent fasting failed because it proved harder to stick with than a calorie restriction diet. More people abandoned the intermittent fast (38% vs. 29%) and ended up switching to conventional diets.

The great innovation in intermittent fasting ended up being its fatal flaw. People are no more likely to stay on it than they were to stay on a run of the mill diet. It doesn't seem to be any worse than simply cutting calories, but it doesn't seem to be any better either.

In the end, eating less is really the only way to lose weight. Whether you do it seems to be more important than how you do it.

So what's the best diet? Ultimately, the best diet, is the one you can stick with.

Christopher Labos is a physician who writes about medicine and health issues. He co-hosts a podcast called The Body of Evidence and tweets at @drlabos.