Amy Reeder is a Certified Diabetes Educator with a master’s degree in nutrition from the University of Utah. She has worked in the diabetes field since 2005 and has been a Certified Diabetes Educator since 2007.
You're probably familiar with the concept of fasting, which is to go without food or drink for an extended amount of time. Fasting is common in many religions around the world, but can it also be a practice for managing your health when done safely and intermittently.
Intermittent fasting means that you greatly restrict calories on certain days of the week and eat normally on the other days of the week. With this plan, your fasting days are either consecutive days or your fasting days alternate with regular eating days. Your fasting days usually total one to three days per week.
What are the benefits of this type of eating plan?
Some studies in fasting animals have shown weight loss, decreased incidence of diabetes, improved blood pressure, and lowered cholesterol. Human studies have illustrated that restricting caloric intake could possibly reverse type 2 diabetes in some people. This research confirmed improved pancreatic function and less insulin resistance in fasting subjects. Fasting days allow the body to use stored energy from the body (fat and glucose).
Note: Fasting studies have only examined the effects of intermittent fasting on type 2 diabetes, NOT other types of diabetes such as type 1 or gestational.
Fasting diet books and programs make big claims that sound appealing, but we need more research to confirm the findings and the benefits of research done to date. It is unclear if intermittent fasting is as beneficial for weight loss and blood glucose management as consistently reducing calorie consumption on a daily basis. However, there is promise for intermittent fasting as an alternative to “dieting” for weight loss and type 2 diabetes risk reduction in the overweight and obese population.
Intermittent fasting allows some flexibility in eating, whereas low-calorie diets can feel restrictive on all days of the week as opposed to just a few. The idea is that for most days of the week (four to six), you stick to consuming a fraction of the amount of calories advised for your gender, body type, and health. For example, on average, caloric intake for men might be 2,500 per day, and for women 2,000 per day. On the days you are fasting (one to three times a week), you restrict your calories to only 25 percent of your regular intake; for example, 600 calories per day for men and 500 per day for women.
An average fasting day might look something like this: steel cut oatmeal with one half cup of blueberries for breakfast, and chicken stir fry with five ounces of chicken and vegetables, and one tangerine for lunch/dinner.
It’s important to include healthy foods not only on fasting days, but also on your non-fasting days!
How to practice intermittent fasting safely
While intermittent fasting could be cost-effective and low-risk for the appropriate population, is it sustainable over time? Will fasting lead to feelings of deprivation, food cravings, or binge-eating?
Those are questions that would need to be addressed individually. We do know that limiting calories means you are also limiting vitamin and mineral intake. If you follow an intermittent fasting program, it is important to consume nutrient-dense foods (as listed above) as opposed to processed “diet” foods in order to feel satisfied and get your vitamins and minerals.
Would intermittent fasting work for you?
Intermittent fasting may be appropriate for people with a BMI greater than 25, prediabetes, or type 2 diabetes not on blood sugar-lowering medications such as insulin, sulphonylureas, or glinides. These medications in combination with intermittent fasting can cause an increased risk of low blood sugar. Because people with type 1 diabetes must take insulin daily, intermittent fasting would be contraindicated because of the increased risk of hypoglycemia.
In relation to diabetes specifically, intermittent fasting can have the benefit of decreasing insulin resistance in people with prediabetes or type 2 diabetes, but it will not necessarily improve blood glucose levels. More human research is needed before we can make specific recommendations for following an intermittent fasting program to treat diabetes or improve overall health.
If you're interested in this approach to diet, speak with your healthcare provider to get his or her perspective and to work out an appropriate plan of action.