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The 5:2 Fasting Diet For Weight Loss

Updated on April 6, 2016
A typical Fast Day meal 250 calories.
A typical Fast Day meal 250 calories.

The 5:2 diet has slowly crept across the pond to North America, and it is gaining momentum. The idea was first presented in an hour long documentary on BBC called "Eat, Fast, Live Longer." This was first aired in Britain during the Summer 2012 London Olympics, which is why the narrator, and guinea pig for several different fasting diets, thought no one would even notice it.

Well ,he was wrong! This has taken Britain by storm, and newspapers frequently publish recipes for the devoted followers. Michael Mosley was trained as a doctor, but has spent the better part of his career covering medical topics for the BBC. He was 53 at the time of filming, and at 5 foot 11, and 187 pounds, did not feel he was unhealthy. Shockingly his doctor had told him he was pre-diabetic, and an MRI for one of his documentaries revealed he had a significant amount of internal body fat. He was thin on the outside and fat on the inside (TOFI), which put him at a higher risk for a multitude of health problems.

This led Mosley on a quest to get healthy, reduce his risk of diabetes and cancer, and lose some of the internal fat surrounding his vital organs. After meeting with many researchers, he ended up settling on the 5:2 diet plan.

Rules and Guidelines

  1. 2 days per week, women eat 500 calories, and men 600 calories only. These are called fast days.
  2. On the 5 other days, eat normally. Women eat 2000 calories, and men eat 2400 calories. These are called feed days. It is not necessary to count calories on these days, just be aware that you are staying roughly within the range. Pay attention to hunger cues and the feeling of satiety.
  3. Try and ensure that the two fast days chosen are not consecutive, as by the 48th hour, you may be tempted to eat your right arm!
  4. The days can vary week to week depending on your schedule.
  5. No foods are off-limits, as long as the calories are within the designated amounts.
  6. Make sure to drink plenty of calorie-free drinks on fast day, preferably water, tea, or coffee. Try not to consume to many diet sodas, as the affect of aspartame can play with insulin production.
  7. The calories on fast day can be consumed over the course of the day, although Mosley prefers splitting them for breakfast and dinner, and leaving 12 hours in between for additional fasting benefits. Some research for the alternate day fast shows people eating all of the calories in one sitting around lunch. Mosley’s co-author Mimi split them into three small meals, and still lost weight.
  8. Try and include some protein on fast days, as there will be muscle loss if none are consumed. Fat and carbohydrates can be stored in the body as fat, but protein cannot be stored.

A Typical Fasting Day

Here are some suggested typical fasting days:

Mosley’s Day

  • Eat two eggs and a slice of ham for breakfast (300 calories).
  • Drink water, tea, coffee, and calorie-free drinks all day, to give a 12 hour fast.
  • Dinner then can be a 300 calorie meal for men, 200 for women—a chicken breast is 150 calories, paired with a mountain of vegetables, or a broth-based soup.

Mimi’s Day

  • Eat 200 calorie oatmeal with blueberries for breakfast (200 calories).
  • An apple for lunch (80 calories).
  • A 200 calorie dinner—half a chicken breast and stir fry veggies, or broth based soup.
  • Calorie-free drinks all day.

My Day

  • Protein shake for breakfast (120 calories).
  • Salad for lunch—2 cups arugula, 4 tablespoons cucumber and red pepper, 10 grape tomatoes, 1 tablespoon sweet onion, 1 tablespoon lemon-garlic vinaigrette (77 calories).
  • 300 calorie dinner.
  • Calorie-free drinks all day.


  • Get creative with your flavor free drinks. Buy a selection of flavored, caffeine-free herbal teas. They can be brewed hot or served over ice. Sweeten with Stevia if required. Try and drink before you develop hunger pangs, and the day will go much more smoothly.
  • Get to know the calorie count on items. Read labels. Download an app! It is shocking how low in calories veggies are, so this will likely make up a good part of fast day. Prepared meals are fine too, and the label will have the calorie total, having done the work for you.
  • Plan out fast day before it happens. Make sure you have the food on hand. I don’t like to cook on this day, but have a family to feed, so I'll often make soups in the slow cooker.
  • My favorite tip is to make a soup, or buy a good quality soup, then for my serving, I add equal parts chicken stock (usually around 7 calories a cup). This ends up cutting the calories in half. For instance, a soup that is 200 calories a cup becomes 103 calories a cup once diluted with stock. This allows you to fill up on two cups of soup for roughly the calories of one.
  • One of my favorite tips I learned from Dr Joel Fuhrman from his book "Eat to Live" is water sautéing. Instead of using oil to sauté vegetables at the beginning of a recipe, you add a couple of tablespoons of water to the pan. This works for starting soups or stir-fries. You can also use a couple of tablespoons of broth from more flavor. I sometimes cover the pan to help the vegetables sweat out.

Green Tea Lime Cooler

Below is a recipe for my favorite calorie-free drink, a green tea lime cooler.


  1. 1 green tea bag
  2. 3 slices fresh lime, washed first
  3. 1 tsp stevia


  1. Pour boiling water over tea bag in mug. Steep 5 minutes.
  2. Meanwhile add plenty of ice, stevia, and squeeze lime into a glass, then drop lime pieces in.
  3. Pour hot tea over the ice mixture, and enjoy!

Free and Helpful Apps

Download an app to make your life easier.

  • Mosley recommends My Fitness Pal, which is a calorie counter and exercise tracker. This helps to track fast day calories.
  • My favorite app is Lose It, which is very similar to My Fitness Pal, but the feature I love is it can scan barcodes to automatically enter the calorie information. The database is huge—it even includes many produce labels. This makes calculating your 500 calories a cinch. I also use it if I am making a recipe. I scan each item to get the total for the whole recipe, then divide by my serving size. I don’t bother tracking calories on my feed days. You can also enter your weights into this program, and email reports to yourself.

Both apps are free, and worth looking into!

My favorite app.
My favorite app.
It was Arugula I was eating!
It was Arugula I was eating!

Weighing Yourself

  • Mosley suggests you don’t weigh yourself too often. Due to the nature of this diet, your weight can fluctuate 2 to 3 pounds each week.
  • My suggestion is to weigh yourself, and take some body measurements on the day you start. I like the bust, waist, hips, thigh, calf, bicep, and a sucked-in-waist as my measurements. Then, weigh yourself the morning after the second fast in the first week (if you fast Monday/Wednesday, then weigh Thursday morning). From then on, weigh yourself every second week the morning after the second fast day for that week.
  • I would take body measurements once per month. I suggest committing to a 5-week program, like Mosley did, and see where you are at, at that point. That is only 10 days of dieting!

Will This Diet Lose if I Only Want to Lose 10 Pounds?

  • Mosley was 187 pounds, and 5'11". For most people, this doesn’t sound like he would need to lose too much weight. He was able to get down to 169 pounds until his wife finally said, "Stop!"
  • Co-author Mimi was only 128 pounds and was able to drop to 119 pounds.

This shows that the diet can easily work even when there is not much weight to lose. Mosley claims that most calorie-reducing diets result in people lose 75% fat, and 25% muscles. The 5:2 diet has been shown to lose 100% fat, roughly 1 pound of fat per week. Maintaining the muscle mass helps keep the metabolism up.

Final Words

If you are lucky enough to reach your ideal weight, but would like to continue fasting for the other health benefits, Mosley suggests switching to a 6:1 plan, where you will fast one day a week.That is what he did, and found the tests showed he was still in the low-risk category for disease due to the low level of IGF1 (insulin growth hormone) in his blood.

Who should not do this diet?

  • Anyone who is pregnant or breastfeeding.
  • Any Type 1 diabetic and most Type 2 diabetics, because fasting can lead to hypoglycemia in these people. Check with your doctor first.
  • Anyone with a history of eating disorders or at high-risk of developing an eating disorder.
  • Underweight people.


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    • kitkat1141 profile image

      kitkat1141 14 months ago from Ontario, Canada

      Hi Mary. Thank you for looking. If Friday is your fast day, you will only have 500 calories all day Friday, including dinner. You will break the fast Saturday morning. I know 500 calories sounds like you will be hungry, but I promise you can avoid those hunger pains by choosing very low calorie but filling foods. 2 cups of arugula have 15 calories, 2 cups of chicken broth have 14 calories. Get a good selection of herbal teas to sip on all day, hot or over ice. I find the next day I get full quickly. I serve up a regular serving size, but usually eat half the amount, and save the other half for later. If you are new to fasting, you could start with 750 calories the two fast days to adjust to eating low calories. Of course your results will be slower. Weight watchers is a perfect accompaniment to the 5:2 diet. Don't forget, there are many other benefits to intermittent fasting like lowering your risk of several cancers, diabetes and Alzheimer's. Good luck. Let us know how it works for you!

    • profile image

      Mary 14 months ago

      I'm hoping you can clarify something for me as far as timing of the 5:2. Hypothetically speaking, if I have dinner at 6pm on Thursday, as a "feast day", then would my "fast day" end at 6pm on Friday, as that is 24 hours?

      I was hoping I would eat dinner Thursday, and then space out the 500 calories throughout Friday, starting at 10am, which would give me 16 hours straight fast, eating 500 calories between 10 and 6, so I could then start my next "feast" day with a healthy dinner Friday night. Is this accurate?

      Or would it go from 6pm Thursday fasting all day Friday with the 500 calories and Saturday morning would break the fast...although that would be closer to 32 hours?

      I am currently doing Weight Watchers, which has shifted to mindful, clean, healthy eating, and would like to incorporate 5:2 into my meal plans each week. I guess I am just confused if a "day" is a 24 hour period, or if a "day" is a calendar "day". Thanks!

    • kitkat1141 profile image

      kitkat1141 4 years ago from Ontario, Canada

      Thanks for looking. Best of luck in your weight loss adventures. I can certainly relate. I gave this diet the 5 week trial like Mosley did in the documentary and lost 11 pounds. I was quite pleased. After the first few fast days, I was shocked how well I could survive a 500 calorie day! This is the first diet I have read about that seems to have so many other health benefits.

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