In recent years intermittent fasting has become the buzzy new kid on the dieting block. But what is intermittent fasting? Does it really work? And is it right for you? Today we will dive into all these questions.
What is intermittent fasting?
Well that depends. Both in the medical literature and in the ley media intermittent fasting refers to several different patterns of alternate periods of eating and fasting. Let’s define the most common regimens:
Alternate day fasting: just what it sounds like, alternate 24-hour periods of eating and not eating
5:2 fasting: reducing calories to 500 or less two days per week
Time restricted daily eating: fasting for 12 to 18 hours daily and eating in the remaining 6-10 hour window
I find my patients are best able to follow a time restricted daily eating pattern with a goal of fasting for 16 hours and eating during an 8-hour window. Most accomplish this by pushing back breakfast to 11 am or skipping breakfast altogether and having lunch at noon. They wrap up dinner by 7 or 8 p.m.
What is intermittent fasting supposed to do?
Intermittent fasting was originally studied for its effects on longevity. Early studies showed rats’ life spans could be increased by up to 80% with alternate day fasting! You won’t be surprised to hear that you probably won’t live to be 120 years old if you skip some meals.
However, studies of intermittent fasting in humans have shown many benefits including improved cholesterol levels, lower blood pressure, improved insulin sensitivity, weight loss and decreased waist circumference. Inflammation is decreased with intermittent fasting, leading to improved resistance to disease. Studies suggest this may help with healing after surgery. There seem to be cognitive benefits too. There are even on-going studies in patients receiving chemotherapy for cancer. So stay tuned, the list of benefits seems to increase daily.
But isn’t breakfast the most important meal of the day?
We all remember hearing that we need food in the morning to fuel us for the day. It turns out that it’s how you break your fast, not when you break it that is important. Traditional American breakfasts of cereal hot or cold (including oatmeal), toast or waffles and pancakes are very high in carbohydrates. They set our blood sugar off on a roller coaster trajectory that makes us hungry, irritable and carb craving.
Break your fast instead with a mixed meal of protein, healthy fats and whole grains and your energy levels will be more stable and carb cravings will not appear. This is as true at 11 am as it is at 7 or 8 am.
Many people are concerned because they wake up hungry. But you don’t have to start time restricted eating all at once. Start with a 12 hour fast (from 7p.m. to 7 a.m. for example) and lengthen your fast by 30-60 minutes each week until you are routinely eating only during an 8-hour period. Hunger and irritability will subside as your body becomes used to your new routine.
Remember intermittent fasting does not apply to calorie free beverages like water, coffee and tea. You should avoid artificially sweetened drinks during your fast as they increase insulin levels and can increase hunger and carbohydrate craving.
Also remember you don’t have to follow intermittent fasting everyday to reap some of the benefits. Many of my patients follow time restricted eating during the week, but give themselves more lee-way on the weekends.
The first step to following intermittent fasting is to check with your physician and make sure it is safe for you. This is especially important for patients taking certain medications for diabetes.
Then set yourself up for success with some planning. When is your typical meal schedule and how will you alter it? What will you eat for breakfast and how will you remember to stop eating at the end of the day. As with all new habits it can be helpful to tell your family, friends or co-workers about your plans so they can support your efforts.
Remember the goal of intermittent fasting is not only weight loss, but to provide a sustainable lifestyle change with many potential health benefits.
If you are interested in the scientific literature on intermittent fasting, there was a great review article in the New England Journal of Medicine on December 26, 2019.