Intermittent fasting is a dietary approach to weight loss that has recently gained popularity. It focuses on limiting the calories you take in for varying periods of time, in a repeating pattern.
There is a wide range of options to this approach. The calorie restriction during the fasting period might range from modest to significant, or even total, as with a water-only fast. The fasting period may be a day or several days. What is allowed during that time depends on the severity of the dietary restriction. This may range from just calorie-free liquids to a combination of fluids, supplements, and foods that result in a much smaller percentage of overall daily caloric intake.
This fasting period is then followed by a day or more with fewer calorie restrictions.
Researchers are now studying the effectiveness of intermittent fasting to lose weight. Any dietary approach that results in weight loss is a result of caloric restriction, caloric expenditure, and the dieter’s ability to follow the protocol.
A diet that is effective will result in long-term and sustained weight loss. But it is important to keep in mind that there are other factors beyond diet that impact those results. Lifestyle and behavioral modifications, including stress management, exercise, sleep, and other lifestyle factors can all impact how effective a diet may be. However, the specific approach to the weight loss, such as intermittent fasting, can impact many of the factors that contribute to long term success.
One of the most important factors in successful and safe weight loss is ensuring you are getting adequate nutrition, meaning all the daily requirements for vitamins, minerals, protein, and more are met. If the calorie restriction and pattern is too severe, it is possible that you will not get the nutrition you need. These nutritional deficits might not only delay weight loss, but they may also cause medical problems.
There are also questions about how intermittent fasting affects the metabolic processes in the body, especially when the fasting is severe. A recent study published in Medical News Today looked at how intermittent fasting may affect the risk of type 2 diabetes. In this animal study, rats were placed on a high degree of intermittent fasting caloric restriction. They were then compared to a controlled non-fasting group. Even though weight loss occurred in the intermittent fasting subjects, there was an increase in abdominal body fat, which is associated with increased insulin levels. There were additional concerns identified as well, including damage to the pancreas and increased insulin resistance.
While animal studies are not always indicative of what might happen in humans, this study does at least raise the question of the safety of this weight loss approach. The high degree of caloric restriction may possibly have negative consequences for people with diabetes or who are pre-diabetic.
Because there is a range of severity of the caloric restriction and the pattern affecting the duration of it, there is potential for medical concern in diabetics, pre-diabetics, and those with certain illnesses requiring medications that affect kidney function, liver function, and more. As a result, anyone considering intermittent fasting should see their physician to discuss any possible risks before starting such a weight loss intervention.
Despite the concerns, there are benefits to this dietary approach.
Findings from studies indicate it may possibly lower the risk of cancer.
From a behavioral perspective, it may be possible to use the concept of intermittent fasting without the severe restriction of calories. A protocol that might limit food by using a nutritional supplement will result in a smaller restriction of calories without sacrificing nutrition on “fasting” days. This may prove to be a safe and helpful method for long term weight management success.
There is significant interest in the use of intermittent fasting to help stem the obesity epidemic in the United States. Further studies will help to define its possible role.
The use of intermittent fasting as a viable, and potentially beneficial, dietary protocol requires further study. If you are considering this approach, please be sure to speak with your physician.
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Dr. Vincent Pera is medical director and program director for the Center for Weight and Wellness.