While intermittent fasting for weight loss has received a lot of celebrity attention, it might surprise you to know it’s been around for decades. Strategies like delaying breakfast or not eating after 7 p.m. are effective ways to limit the amount of time spent eating, thus saving calories, resulting in weight loss. Both of these options result in a period of food restriction of about 12–16 hours — an intermittent fast. And while this might sound extreme — you’re likely asleep for at least half of it.
Evidence continues to mount that intermittent fasting for weight loss can work for the long term, if it’s a plan that connects with you. By making healthy food choices, intermittent fasting can be a safe and effective weight-loss tool for both the short and long term. In fact, this term “intermittent fasting” might be better referred to as “intermittent eating,” because it’s not about deprivation, it’s about boosting mindful eating and a new relationship with food.
Intermittent fasting won’t automatically make you a healthier eater, and will only promote weight loss if fewer calories are consumed weekly, over time.
The types of intermittent fasting diets:
The two main ways to do this are by time-restricted eating (choosing an up to 12-hour period of eating daily) and a 5:2 plan (two days of limited calories of about 500 calories, and moderate intake on the other five).
Like any weight-loss plan, always check with your doctor before making any significant changes in your eating, especially if you have a chronic illness, or take prescription medication. And the ease of intermittent fasting is that you can choose from any balanced eating plan from WW to vegan because you are only modifying the times for eating, not the actual foods.
Why intermittent fasting works:
Whatever plan appeals to you, here are some top reasons why this approach can help reduce daily caloric intake:
- Reconnects you with true, biological hunger (not emotional, “head” hunger)
- Makes it easier to recognize contentment and fullness, to stop eating sooner
- Provides daily structure
- Breaks the habit of snacking and all-day “grazing”
- Helps you accept the slight discomfort of being a little hungry
And the downside? It’s always possible to “eat around” either plan, and overeat at certain times, cancelling out any calorie savings and weight loss. But at the same time, learning a mindful approach to eating will help keep you on track.
Here is some simple advice to optimize time-restricted intermittent fasting for weight loss:
- Choose the most realistic 8-12-hour eating period
- Aim to stop your evening eating by 9 p.m. (or at least two hours before bedtime)
- Pre-plan your eating intervals for at least two meals
- Limit snacking (two snacks per day, if desired)
- Be mindful of portion size
- Stay hydrated with low-calorie beverages
- Be flexible: Choose a snack of 100-200 calories if you get physical signs of hunger (headache, light-headed)
- Consume a varied diet, with lots of fruits and vegetables, moderate amounts of lean protein, healthy fats, low or non-fat dairy; add whole grains if including starchy carbohydrates
- Choose produce as the primary source of carbohydrates, limiting starchy carbohydrates like bread, rice, pasta, potatoes and cereal
- Allow yourself a “treat” food daily of around 100 calories
If you're interested in following the 5:2 plan, here is advice to make it more manageable:
- Focus primarily on lean protein (eggs, fish, low-fat dairy, poultry, lean red meat) on the low-calorie days
- Be mindful on your “standard eating” days
- Maintain structure to avoid overeating
- Aim for three meals; snacks are optional and limited to two per day
- Choose a varied eating strategy similar to the time-restricted plan
- Ease into the restricted days, to find your optimal amount of daily calories (it might be 600 or 700 calories)
- Stay hydrated with low-calorie liquids
- Be flexible if physical hunger strikes (headache, light headed, fatigue) and choose a 100-200-calorie snack
Intermittent fasting works best if you are already a healthy eater, and want some structure to eat smaller portions less often. If you're are a grazer or snacker and want to consolidate and compress your eating, it can also be a good option. Finally, if you’re not in touch with your body’s hunger and fullness signals, intermittent fasting could be a good way to reconnect with your hunger cues.
Remember that this plan will work best for weight loss if you are already making smart, nutrient-rich choices. If you’re not a particularly healthy eater, it’s better to make dietary changes and practice those before adjusting the timing of your eating.
This plan is most definitely not for you if you have anxiety over periods of complete food restriction (and low-calorie drinks don’t help), or have not been cleared by your doctor to give it a try.
If intermittent fasting sounds appealing to you, including the caveats, there’s no harm in trying. As with all weight-loss plans, it will work for some, but not all, people. And, if after a few weeks you find it’s not a good fit for you, then switch to something more compatible with your eating style.
Madelyn Fernstrom, PhD is the NBC News Health and Nutrition Editor. Follow her on Twitter @drfernstrom.