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What is the Alternate Day Diet?

By B. Williams
Updated Feb 25, 2024
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Dieting can be both stressful and a challenge for many people, especially when there are so many diet plans, many of them fad diets, from which to choose. The alternate day diet plan, also commonly referred to as the Johnson upday downday diet, is a popular dieting option with dieters because it allows dieters to eat as much as they want of whatever foods they want one day while essentially fasting the next day. The cycle continues for as long as weight loss is desired.

Developed by Dr. James Johnson, the alternate day diet is based on research that found that those animals that eat between 30 and 40 percent fewer calories than they normally would tend to have an increased lifespan, living up to 40 percent longer than those animals who had a normal daily caloric intake.

Encouraged by those findings, Dr. Johnson created the diet, which is said to increase the dieter’s metabolism thus allowing the dieter to burn calories faster which, in turn, will lead to faster weight loss. Generally, however, lower calorie diets result in a slowing of the dieter’s metabolism.

The alternate day diet calls for dieters to eat as much as they want one day, typically referred to as the up day. While dieters can eat whatever foods they want and as much as of those foods as they want, they should not purposely stuff themselves. However, it’s important that dieters feel satisfied on up days.

The following day, also known as the down day, dieters are to cut back their caloric intake to between 300 and 500 calories. The US Food and Drug Administration (FDA) bases nutritional information on a 2,500 and 2,000 calories per day diet, but depending on your activity levels and Body Mass Index (BMI) your appropriate daily intakes may be much different.

For the first two weeks of the diet, dieters are advised to only consume protein shakes on their down days. After the first two weeks on the alternate day diet, dieters can begin to eat food on their down days, provided they keep their caloric intake to 500 calories or less.

However, not everyone believes this diet is a safe or an effective way to lose weight, with some opponents asserting that it is a fad diet that is strikingly similar, with its binging one day and fasting the next day, to bulimia. Many opponents believe that a balanced diet is essential to weight loss rather than dieters resorting to fad diets like the Johnson upday downday diet.

In addition, some who have tried the fad diet have reported feeling tired, lightheaded, and hungry on their down days. The side effects of the alternate day diet will likely vary from dieter to dieter.

Before trying a new diet like the alternate day diet, dieters should always consult their physicians to discuss whether they are healthy enough to diet and to discuss the advantages and disadvantages of a particular diet.

WiseGeek is dedicated to providing accurate and trustworthy information. We carefully select reputable sources and employ a rigorous fact-checking process to maintain the highest standards. To learn more about our commitment to accuracy, read our editorial process.
Discussion Comments
By anon225475 — On Oct 27, 2011

I like this diet. Just like anon, I find it easier to just fast on the down days. It cuts back on cravings and temptation. I've already lost 10 pounds in a month. I tried the diet with eating on the down days and counting every calorie in a journal for both days, but I found that the more I ate, the more hungry I became, and the more obsessed with food I ended up being. Now I eat whatever I want and whatever quantity I please on the up day and I fast on the down day.

It's working for me. Here's to another month of success hopefully.

By anon149815 — On Feb 05, 2011

I've tried several diets and have fallen by the wayside. This is the only one that I feel I can stick to for any length of time. This is my fourth straight week, and I've slipped up and just re-started the next day. I don't even take the 500 calories, I find it easier to just fast on the down days. I still exercise and I'm losing and actually keeping the weight off. I love this diet. Eat sensibly on the up days and there is no need to worry about lack of nutrients.

By anon115683 — On Oct 04, 2010

this diet is the only diet that works for me. i am so tired of hearing people badmouth this diet. most of the people who criticize this diet have not even tried it for themselves. i have tried many diets, and this one is the best for me.

on the feast day, you are able to eat whatever you want, but you will actually not be that hungry. the toughest part is sticking to the diet day, but the results are worth it and you will be easily motivated to just wait until tomorrow to have that piece of cake. and of course you cannot eat whole cakes and pies on the free day, but you can have a piece of your favorite cake along with your regular meals.

By grammymc — On Apr 25, 2009

After the Induction Phase, Dr. Johnson states you should eat 500 calories. Then after that the down day calories can go up from there. How much they go up is determined by you and how fast you want to lose.

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