Learn how intermittent fasting works, explore popular methods like 5:2 and time-restricted eating, and find out if this approach fits your lifestyle.

Intermittent fasting (IF) involves going for some period of time—from a few hours to a few days—eating little (as few as 500 calories per day) to no food at all. It’s a pattern of eating based on time limits. For a set number of hours or days, you eat a typical diet. At the end of that period, you switch to very few or no calories—this is called fasting. 

The idea is that IF prompts the body’s cells to shift gears: instead of focusing solely on digestion, they can redirect energy toward repair and more efficient energy use. That’s why IF is often promoted for its potential to improve body composition (through fat loss and reduced waist circumference) and to support markers of health such as blood pressure and cholesterol levels. 

What Research Says 

When it comes to IF, research varies. Some studies show no benefit, while other studies show improvements in the following markers when compared with no intervention. 

  • Better blood sugar control 
  • Lower fasting insulin levels 
  • Weight and waist circumference reduction 
  • Improved lipid levels (triglycerides, LDL cholesterol) 
  • Lower blood pressure (systolic) 
  • Reduced chronic inflammation 
  • Increases in HDL (“good” cholesterol) and fat-free mass 

TYPES OF INTERMITTENT FASTING: 

If you’re curious about trying IF, there are a few common approaches. Some are highly structured, while others offer flexibility: 

  • 16:8 Method 
    This is the most widely used version: you fast for 16 hours and eat within an 8-hour window (for example, 12 p.m. to 8 p.m.). It works especially well if you naturally skip breakfast. 

Real-world tip: Most people end up following gentler versions, like 14:10 or even 12:12 (say, eating breakfast at 8 a.m. and finishing dinner at 8 p.m.). These more flexible schedules are often easier to stick with long-term while still offering benefits. 

  • 5:2 Intermittent Fasting 
    For five days of the week, you eat anything you want, and then for the remaining two days, you fast. In this plan, fasting is defined as consuming just 500 calories for the entire day for women and 600 calories for men. Studies show that the 5:2 approach can support modest weight loss and improvements in blood sugar control, though it’s generally no more effective than standard calorie-restricted diets. 
  • Alternate-Day Fasting 
    One day, you eat whatever you want (from 8 a.m. to 8 p.m. only), and the next day you fast, repeating this alternate pattern for as long as desired. Here, fasting means only 500 calories for both men and women. 

Takeaway: Intermittent fasting doesn’t have to be all-or-nothing. Even something as simple as “closing the kitchen after dinner” can be a great first step. 

Like most weight loss plans, there are pros and cons. Here’s a quick look at both sides: 

POTENTIAL BENEFITS OF INTERMITTENT FASTING 
On the positive side, some research suggests IF can help with weight loss. When you limit the number of hours you eat, you’re effectively clipping off calories from your daily total. Put simply, fewer calories = weight loss. (But of course, this is true of all calorie-controlled diets, and there’s limited evidence that fasting is better than traditional calorie-restrictive plans.) 

IF may also: 

  • Support blood sugar control and reduce diabetes risk 
  • Improve heart-related markers such as cholesterol and triglycerides 
  • Encourage more mindful eating—many people find they savor their food more when calories are limited 
  • Lead to better food choices, since you’ll want to “spend” limited calories on nutrient-dense options like lean proteins, veggies, and whole grains 

On fasting days, you’re more likely to savor every bite and chew more slowly. In other words, you’ll actually taste your food (versus gobbling it down). 

And with so few calories to spend, you’ll want to make the most of them. Instead of eating 600 calories worth of salami or cookies, you’ll want to choose nutrient-packed lean chicken, broccoli and eggs and drink lots of water. It’s absolutely critical to choose foods that fuel energy and provide vitamins, minerals and antioxidants. 

Finally, because you’re trying to lose weight, you’re likely to make thoughtful choices on your “non-fasting” days, as well. Overall, you’ll learn a very important lesson: Every bite counts. 

POTENTIAL DOWNSIDES AND RISKS 
No surprise here, but fasting is linked to hunger, which can lead to overeating. This can happen—you are so proud of yourself for making it through the fasting part, you wind up overeating or binging on the non-fasting days, which will most definitely cancel out all hopes of weight loss. 

Here are some of the other IF challenges: 

  • Low energy, irritability, headaches, and mood swings are common complaints 
  • Constipation may occur due to dietary changes 
  • Some evidence suggests IF may affect the menstrual cycle in certain women 

And let’s face it, this type of plan runs counter to the way most of us have learned to eat. We’re used to fueling throughout the day, every day. We wake up and eat breakfast. Meet friends for lunch and enjoy family meals together. Food is fuel, food is friendship, food is family. 

Who Should Avoid Intermittent Fasting 

While intermittent fasting can be safe for many people, it may not be a healthy pattern if you: 

  • Have a history of eating disorders 
  • Are pregnant or breastfeeding 
  • Are at high risk of bone loss and falls 
  • Have diabetes (especially if on medication) 
  • Take medications that require food intake 
  • Are an adolescent 

Is Intermittent Fasting Right for You? 

There is nothing inherently magical about the strategy, but it can be an effective means of controlling caloric intake, and thus, help with weight loss. And it can be used in conjunction with other eating styles, like Paleo, low-carb, low-fat, vegetarian… since it focuses on when you eat, not necessarily what you eat. 

However, intermittent fasting is certainly not for everyone. If fasting leaves you feeling irritable, lightheaded, or prone to overeating, it may not be the right fit.  

And, as with any diet change, make sure to check in with your doctor first, especially if you take medication or have an underlying medical condition. 

Eating and Drinking Tips for Intermittent Fasting 

If you decide to try IF, what you eat before your fasting window, and what you drink during it, matters. 

What to Eat Before Fasting 

Choose a balanced, filling meal that digests slowly to keep you steady and satisfied: 

  • Proteins: chicken, fish, eggs, Greek yogurt, tofu, lentils 
  • High-fiber carbs: veggies, fruit, oats, quinoa, lentils, whole-grain bread & pasta 
  • Healthy fats: avocado, nuts, seeds, olive oil 

Meal ideas: 

  • Veggie omelet with avocado toast 
  • Chicken & broccoli stir-fry with quinoa 
  • Baked salmon with roasted vegetables and sweet potato 

What to Drink While Fasting 

Hydration is key for energy and hunger management. Stick with non-caloric beverages that won’t break your fast: 

  • Water (still or sparkling) 
  • Plain tea (herbal, green, or black) 
  • Black coffee (no milk or sugar) 

Avoid: juice, soda, alcohol, and anything with calories—including creamers and sweeteners. 

Intermittent fasting can offer benefits, but it’s not a one-size-fits-all solution. Finding an eating style that supports your health and feels sustainable is what matters most.