Intermittent Fasting


Exploring Potential Benefits and Drawbacks

Story by Annie Eller, RD LD   |

Intermittent fasting (IF) is a popular topic in the health and wellness space as of late. However, this is not a new concept. Fasting has been practiced for centuries for spiritual and other cultural practices. As far back as the 5th century BCE, it has been noted that Hippocrates recommended abstaining from food and drink for therapeutic purposes.

IF has also become an important topic in research. Many researches have been hopeful in using IF as an intervention for weight loss and other health benefits. Fasting is a more nuanced approach to weight loss, but has sparked interest of some clinicians who are looking for new recommendations to help their patients.

So is intermittent fasting worth trying? As with most nutrition matters, the answer is, it depends. Before changing your diet or eating pattern in any capacity, it is important to ask yourself three important questions; What am I trying to achieve? Is this a sustainable change? Will this negatively impact me physically or mentally? It’s easy to hear excitement about different diets and think it’ll solve all of your health concerns, but try to remember nutrition needs (and meal timing for that matter) is different for everyone.

Let’s define what intermittent fasting actually is before diving into what the potential benefits are. The more common regimens are alternate day fasting, such as 2 days of fasting and 5 days of normal eating, or daily time restricted feeding such as only eating in a 6 or 8 hour window of the day. No food is consumed during the fasting periods, however water, black coffee, and herbal tea can be consumed as they are noncaloric. It is important to note, intermittent fasting only defines when to eat but does not dictate what to eat.

As you might expect, research has shown both benefits and limitations of intermittent fasting. Below is the current findings.


It seems intuitive that intermittent fasting will lead to weight loss, but this only holds true if individuals reduce their overall calorie intake. If calories are consumed during excess during the eating window, weight gain can still occur even if someone is fasting for a portion of the day or week. Long story short, research shows us that individuals have equal weight loss success with intermittent fasting versus daily reduced calorie intake as long as in both scenarios they are in a caloric deficit (eating less than they burn off). There are however seemingly promising research outcomes regarding other health benefits with IF. Research shows that even if an individual does not lose weight while fasting, they can have lower blood insulin levels, less evidence of insulin resistance, and lower blood pressure. These are all great markers of reducing risk of chronic diseases such as diabetes and heart disease.


Most human studies have been conducted over shorter periods and therefore don’t show long term impacts of IF, such as on lifespan/longevity. Additionally, more research is needed to see the impacts of fasting on healthy weight individuals or younger/older individuals. Most studies have been conducted on middle aged, obese research participants. Lastly, as with all diet interventions, there are drawbacks regarding participant compliance. With 24/7 access to food and the common eating pattern of three meals + snacks every day, the shift to fasting can be difficult. In human studies, it has been documented that participants struggled to stick to the fasting period due to feeling hungry, fatigued, moody, etc.

How To Apply This To Your Life

So there are certainly documented benefits of intermittent fasting. This doesn’t mean that it will be safe and sustainable for everyone. For example, individuals taking medication based on the timing of their meals (especially insulin) should not jump into fasting without consulting their physician. Additionally, those with a history of eating disorders would not benefit from this approach as it requires a restriction mindset. It is also important to note that individuals still need to follow a nutrient dense diet while practicing IF, including plenty of fruits, veggies, legumes, lean protein, and whole grains. The eating window cannot become a timeframe to “eat whatever” which might become the mindset after fasting. Finally, everyone should consider if fasting will work for them long term. If the approach is not sustainable, work to find another route that will be more likely to last for life. The benefits only last as long as the behavior does.

Bottom Line

Nutrition is very individualized. Not one approach will work best for everyone. For some, intermittent fasting can be a simple way to reduce calorie intake and increase awareness of eating habits. For others, following a nutritious diet while watching portion sizes can be more effective than having a defined eating and fasting periods. Always consider what your goals are and what will work best for you. Lastly, work with a dietitian and your physician to create a plan that will be safe and effective long term. 

Sources: National Institute on Aging and the US National Library of Medicine National Institutes of Health.