File under trends that won’t go away: the 5:2 diet, a type of intermittent fasting made popular by British broadcaster Michael Mosley and late-night host Jimmy Kimmel. Proponents claim it can decrease risk of chronic disease and promote weight loss. Plus, a few studies have linked fasting to longevity, which means you could get a few more days or years on Earth — just to spend them (mostly) not eating.
The 5:2 diet is not for everyone. Jimmy Kimmel himself recently admitted he stopped following the plan that he helped make famous.
“When I started working out is when it came to an end because I was just ravenously hungry,” he said on the podcast “Conan O’Brien Needs a Friend” on May 6. Here’s what you should know before you try fasting two days every week.
What is the 5:2 diet?
The 5:2 diet is a type of fasting where followers eat about 25% of their recommended calorie needs (about 500-600 calories) on two scheduled fasting days and then eat normally the other five days that week. People generally intersperse their fasting days (like planning them for Mondays and Thursdays) so they’re not back-to-back.
Some followers take the 5:2 diet to an extreme by consuming zero calories on their fasting days. Others place restrictions on their non-fasting days by following a high-fat, ketogenic diet.
What can you eat on the 5:2 diet?
There aren’t any hard-and-fast rules about what to eat on the 5:2 diet. Generally, people will eat lower-calorie foods on their fasting days. These could include vegetables, fish, soup, eggs, and lean meat, plus zero-calorie beverages like water and black coffee or tea.
Can you lose weight on the 5:2 diet?
It depends. The theory is that intermittent fasting (IF) limits the opportunities for eating and you’ll lose weight by simply by taking in less calories overall. That’s because many of us eat based on scenario, not hunger levels.
For example, if you’re fasting during your Tuesday meeting that always includes fresh donuts, it may prevent you from eating a higher-calorie food you would’ve had otherwise. However, you could likely achieve the same goal by having a healthy snack about 30 minutes before your meeting and opting out of deep-fried, doughy treats simply because you’ve had something more nutritious ahead of time.
A 2017 study published in the Journal of the American Medical Association found that intermittent fasting didn’t help people lose more weight than traditional methods. Participants who practiced alternate-day fasting and those who simply restricted calories daily lost virtually the same amount over a one-year period.
If you’re trying to lose weight, start by planning when you’ll eat — I talk a lot more about this in my book, Dressing on the Side (and Other Diet Myths Debunked). Having too many options and too much time to decide what we’re eating in a given day can leave us susceptible to making snap decisions that ultimately leave us dissatisfied — either immediately, or when done consistently over time. Pick out your meals and snacks (as you would your outfit for the day) the night before, so you can make choices that support your health goals. Even if you don’t stick to the exact plan, you’ve got a general framework to work with.
Is the 5:2 diet good for your health?
Fasting can negatively impact your health. The same 2017 trial mentioned above — arguably the best to date that looked at humans, not lab animals — also found LDL or “bad” cholesterol levels significantly increased in the alternate fasting day group compared to the control groups.
Going for prolonged periods without eating can also prime you to overeat, creating a cycle that’s difficult to get out of because fasting can mess with our body’s hunger cues and metabolism. Other research has linked fasting with increased risk of depression and anxiety.
The Bottom Line
To make better choices for health and weight loss, it’s simply not feasible for many of us to restrict food for days at a time. Life is too short to cut the number of days you’re “allowed” to eat in a calendar year from 365 to 261 — especially if it stops you from doing other beneficial things, like getting regular exercise and enjoying meals with people you love. There’s more to nourishment than calories, so consider that before buying into any trendy diet or eating plan. Remember that, and you’re already on the right track.
Director, Nutrition Lab
A registered dietitian with a Bachelor of Arts degree from Northwestern University and a Master of Science degree in Clinical Nutrition from New York University, Jaclyn “Jackie” London handles all of Good Housekeeping’s nutrition-related content, testing, and evaluation.