What is the 5:2 diet?

The 5:2 diet has been receiving a lot of attention lately because of its possible connection to weight loss. But what is it, and how does it work? Is it something that MD Anderson dietitians would ever recommend? 

Read on for the answers to these questions and more. 

What is the 5:2 diet?

The 5:2 diet is an eating plan created by a British journalist, author and producer who studied medicine, but then opted for a different career path.  

It’s called the 5:2 diet because for five days out of any given week, you eat normally. On the other two, women are asked to limit themselves to 500 calories per day and men to limit themselves to 600.  

The 5:2 diet has been called a form of intermittent fasting. Is that accurate?  

No. Technically, fasting means abstaining from eating completely for a certain period of time. But people sometimes mistakenly call it that because the amount of food you eat on those two days is not enough to meet your body’s basic needs.  

Does drinking plain water count as breaking a fast?  

No. But any type of beverage with calories does, so sugary sports drinks, lattes, smoothies and carbonated waters sweetened with fruit juice are all out.  

How does the 5:2 diet theoretically work?

The 5:2 diet is just another calorie-restricted diet. And it’s very restrictive on those two days. So, I would not personally recommend it.  

But some people find it easier to eat normally on five days and then cut back on only two. They feel like if they can manage their calorie intake and make it through those, then they’re good. 

How long does it take for the 5:2 diet to start working? 

That depends entirely on the individual: their medical history, genetics, and what they eat on their “normal days.” People don’t all lose weight in the same way or at the same rate. So, in that way, at least, it’s no different from any other calorie-restricted diet.  

What does a typical day look like in the 5:2 diet? 

Again, this is not something we would recommend. But if you’re determined to try it, just keep in mind that “eating normally” doesn’t mean you can binge and eat whatever want on those five days.

You still have to aim for a balanced, healthy diet, rich in whole grains, vegetables and fruits with lean protein.  

On the two “fasting” days, it’s probably best to focus on eating really nutrient-dense foods, like leafy greens, whole grains and lean meats, to ensure that you’re getting as many nutrients as possible. Whole foods and lean proteins will also help you feel full for longer, so you can make it through those long “fasting” days. 

One of the detriments of this type of diet is that it doesn’t take the nutritional side of things into account. While it does cut calories and may ultimately be beneficial for weight loss, it’s really hard to stay healthy when you have fewer opportunities to eat the things your body needs to thrive. And, that can negatively impact your gut microbiome and bowel regularity, among other things.  

That’s why we recommend a consistent, healthy diet with a variety of whole, plant-forward foods.  

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