What To Know About the 5:2 Diet

There are a lot of diets out there. And finding a healthy eating plan that works for you among all those options may seem impossible. The search may involve a lot of trial and error.

Intermittent fasting is a popular eating plan that can be effective for weight loss. It involves alternating periods of fasting with unrestricted (but healthy) eating. And there are many ways to do intermittent fasting.

One way is a 5:2 diet plan.

Registered dietitian Julia Zumpano, RD, LD, gives the 101 on the 5:2 diet and the pros and cons to consider before you adopt it.

What is the 5:2 diet?

In a 5:2 diet, you eat “normally” five days out of the week. These are your non-fasting days. The other two days are fasting days. You consume fewer calories on those days depending on your sex recorded at birth:

• 500 calories for women
• 600 calories for men

You may think it would be best to eat normally for five straight days and then reduce your calories for two straight days. But that’s not ideal.

“When you create your 5:2 schedule, try to separate fasting days as much as possible,” Zumpano says. “An ideal spacing would be to allow two to three days of non-fasting days in between the fasting days. It is essential to allow for at least one non-fasting day in between.”

What to eat on the 5:2 diet

Beyond the restricted-calorie days (fasting days), the 5:2 diet doesn’t specify how or what to eat.

“That provides a lot of flexibility. But it might also leave you wondering what to eat to make sure you get the nutrients you need,” Zumpano notes.

What to eat on fasting days

On fasting days, Zumpano recommends low-calorie, nutrient-dense foods. Focus on lean protein and non-starchy vegetables. These foods provide nutrients and fiber that:

• Aid digestion.
• Manage blood sugar.
• Help you feel full longer.

Foods to avoid on fasting days include:

• Caloric beverages. That includes alcohol and coffee drinks that include foods like sugar, milk or cream. Plain black coffee is OK.
• Carbohydrates, such as breads, pasta, rice, potatoes and most fruits.
• Fats, including butter, oils, nuts, sauces and condiments that are high in fat.

How you consume calories on fasting days is up to you. You might split your calories into two or three small meals or have a combination of meals and snacks.

“For a filling 250-calorie meal, try a piece of white fish about the size of your palm and four cups of spinach, or a bowl of chicken and vegetable soup,” Zumpano suggests. “You could also have a 150-calorie protein shake as a mid-day snack and still have 100 or 200 calories left for the rest of the day.”

Try this Italian vegetable soup recipe. Add chicken for protein or enjoy with chicken breast on the side.

What to eat on non-fasting days

What you eat the other five days of the week matters, too. To realize the full benefits of the 5:2 diet, stick to your recommended number of calories and eat as healthy as possible.

Foods to enjoy on non-fasting days include:

• Fruits and vegetables.
• Lean proteins.
• Legumes, including beans and lentils.
• Low-fat and nonfat dairy products.
• Nuts and seeds.
• Whole grains.
• Healthy fat, such as extra virgin olive oil, nuts and seeds

Can the 5:2 diet really help you lose weight?

In theory, the 5:2 diet creates a calorie deficit that helps you lose weight. Research backs up this theory.

One review evaluated studies of different intermittent fasting plans — including the 5:2 diet. It found that all plans helped people lose weight. The weight loss was about the same as with a traditional calorie-restricted diet that didn’t include intermittent fasting.

Pros and cons of the 5:2 diet

No one eating plan is right for everyone. Let’s take a look at some pros and cons of the 5:2 diet.

Pro: It’s easy to follow

Because you don’t have to count calories every day, it’s a simplified plan. That can make sticking to the diet easier, which is what really matters at the end of the day.

“When you compare popular diets, most can be effective for long-term weight loss — but only if you follow them,” says Zumpano.

Pro: It’s customizable

You can decide which days you fast and what foods you eat. There’s no specific guidance telling you to eat foods you don’t like or can’t get easily.

Pro: It offers other health benefits

Studies on intermittent fasting suggest a range of potential health benefits, although there’s limited data on the 5:2 diet itself.

“Research shows that intermittent fasting affects various body systems and processes,” Zumpano agrees. While more research is needed to understand the full picture, scientists think intermittent fasting may help:

• Boost gut health.
• Enhance brain function and lower your risk of neurological disorders.
• Lower inflammation and joint pain.
• Prevent the progression of Type 2 diabetes by improving how you respond to insulin.
• Reduce your risk of heart disease.

Con: You may overeat on non-fasting days

One of the biggest challenges is not consuming too many calories on non-fasting days. “The hunger from fasting can carry over into the next day,” Zumpano cautions.

Con: It can lead to nutritional deficiencies

If you’re not paying close attention to what you’re eating, you could miss out on important nutrients. For example, there’s little room in the diet for healthy fats on fasting days. So, you need to make up for that on non-fasting days. Salmon, nuts and seeds are good sources of healthy fats.

A multivitamin can also help replace missing vitamins and minerals. But they may cause nausea if you don’t take them with enough food. When possible, it’s best to get the nutrients you need from your foods, Zumpano advises.

Con: There’s no guide for what to eat

The simplicity of the 5:2 diet can be both a pro and con. Yes, it’s easy to follow. But the lack of guidance on what to eat can make it easy to eat the wrong foods.

Consuming less nutritious and inflammation-triggering foods can wipe out the benefits of the 5:2 diet and your overall success. Zumpano recommends avoiding these foods, which include:

• Chips and other unhealthy snacks.
• Commercial baked goods.
• Fast food and deep-fried foods.
• Soda and other sugar-sweetened beverages.
• Ultra-processed foods.

Con: You may not feel great on fasting days

In addition to being hungry, people on the 5:2 diet report a range of symptoms on fasting days, such as:

• Fatigue.
• Headaches.
• Irritability.
• Poor concentration.
• Lightheadedness or dizziness.

Zumpano says a lack of electrolytes can cause some of these symptoms. So, it can help to supplement with an electrolyte-enhanced water.

Easing into the diet slowly can also help. Start by limiting to 900 to 1,000 calories on fasting days to ease in. Then, cut back in increments of 100 to 200 calories until you reach your goal of 500 to 600 calories.

But if you’re feeling unwell, listen to your body and eat something. Over time, you may get used to fasting — but not everyone does. If your symptoms continue, it’s probably time to try a different eating plan or talk to a healthcare provider.

Con: It’s not for everyone

The 5:2 diet may not be if you:

• Are pregnant or breastfeeding
• Have disordered eating, underweight or undernutrition
• Have unmanaged diabetes or other chronic health conditions

If any of these situations apply to you, check with your provider before starting a new eating plan.

The most important factors for choosing a healthy meal plan are sustainability and making sure it doesn’t negatively impact your health.

If that’s the 5:2 diet, great! But there are plenty of other healthy weight-loss diets to experiment with, too, including the Mediterranean diet. With a little time, patience and help from a healthcare team, you’ll find an eating plan that works for you.

Before beginning any new diet, talk with a healthcare provider, like a primary care provider or registered dietitian. They can help advise you on the best options for you.