Intermittent Fasting: Pros and Cons According to NUNM

With so many fad diets out there, and some with very little science to back them up, it can be difficult to discern what is right for you. Join NUNM’s nutrition program, as we take a look at popular weight loss diets and break down the science of what is happening in your body if you choose to partake.  Alexander Bear, Master of Science in Nutrition student, discusses the scientific benefits and potential dangers of intermittent fasting. 

What is Intermittent Fasting?

Intermittent fasting (IF), or time-restricted feeding, simply refers to the period of time that occurs between eating meals. This period of non-eating could be minutes, hours, days, or even months, although the term typically implies a longer period of fasting than 1-3 hours and shorter than 3 or more days.

There are a variety of different approaches for intermittent fasting. The most appropriate method is dependent on what works best with an individual’s schedule, goals, and what is most medically-appropriate. One common method is to skip breakfast and to eat dinner before 7 PM. In this method, there would be a daily 16-hour fast. Another common method is a 24-hour fast.

Potential Benefits of Intermittent Fasting[1][2]

• Improved digestion
• Reduced food cravings
• Increased mental focus and concentration
• More stable energy levels
• Improved mood
• Fat loss
• Decreased inflammation
• Heart disease prevention and management (i.e. decreased blood pressure, heart rate, lowering LDL “bad” cholesterol)
• Prevention and management of Type-II diabetes (i.e. improved insulin sensitivity, better blood glucose regulation)
• Dementia, Alzheimer’s Disease, and Parkinson’s Disease prevention and management

Generally, the benefits of fasting are dependent on the length and timing of the fast. If you allow three hours between meals, the migrating motor complex will be able to complete a full cycle in which residual undigested material is swept through the digestive tract.[3] Therefore, even a few hours of fasting may improve digestion.

During these few hours, the body may begin to run low on circulating glucose to meet its energy needs. This drop in blood sugar will likely prompt you to eat; but, if you extend your fast, the body begins pulling on its stores to maintain blood sugar levels initially. After 48-72 hours, the body begins utilizing stored fats as its primary fuel source along with ketones which are derived from fats.[4] Therefore, more fat loss typically occurs during extended periods of fasting. And because sugar is not being consumed, there is less circulating insulin, and the cells may become more sensitive to insulin.

Timing Your Fasting Period

Another important consideration for intermittent fasting is timing. Our digestive system works most efficiently on a regular cycle. New research has shown that melatonin, which is produced after the sun goes down and promotes sleep, sends signals to the liver to slow its activity.[5] The liver has over 500 known functions, including bile production, which is vital for the digestion and absorption of fats. Therefore, if the intermittent fast restricted foods during all hours of darkness, it may be more effective in terms of digestive benefits than if foods were not restricted at nighttime.

Is Intermittent Fasting Good for Everyone?

Intermittent fasting is generally safe for most people, although there are certain groups of individuals in which intermittent fasting could prove harmful or even fatal. These include:

  • Individuals that are severely malnourished or underweight
  • Individuals with disordered eating or eating disorders
  • Children under eighteen years of age
  • Pregnant and breastfeeding women
  • Individuals, such as diabetics, taking medications affecting blood sugar
  • Individuals with chronic health conditions, especially those that reduce kidney function
  • Individuals with inborn errors of metabolism (e.g. OTC gene variants that cause OTC enzyme deficiency, fatty acid oxidation disorders, carnitine shuttling defects, etc.)

NUNM’s Conclusion on Intermittent Fasting

It is always best to consult with a qualified healthcare professional before making dietary changes, even if you are just changing the timing of when you eat foods. They can help you determine if intermittent fasting would be beneficial for you. This is especially important for longer-term fasts in which vitamin and mineral depletion may occur. It is important to understand that our bodies are incredibly intelligent. If food is restricted at one meal, the body can increase hunger and the amount of calories consumed at the next meal, and even slow down metabolism to match calorie consumption. Intermittent fasting has many potential health benefits, but it should not be assumed that if followed strictly it is guaranteed to produce enormous weight loss and prevent the development or progression of disease. It is a useful tool, but many tools may need to be implemented to help in achieving and maintaining optimal health.


  1. Patterson RE, Laughlin GA, Sears DD, et al. INTERMITTENT FASTING AND HUMAN METABOLIC HEALTH. J Acad Nutr Diet. 2015;115(8):1203-1212. doi:10.1016/j.jand.2015.02.018[1]
  2. Aly SM. Role of Intermittent Fasting on Improving Health and Reducing Diseases. Int J Health Sci. 2014;8(3):V-VI.[2]
  3. Deloose E, Janssen P, Depoortere I, Tack J. The migrating motor complex: control mechanisms and its role in health and disease. Nat Rev Gastroenterol Hepatol. 2012;9(5):271-285. doi:10.1038/nrgastro.2012.57x[3]
  4. Secor SM, Carey HV. Integrative Physiology of Fasting. Compr Physiol. 2016;6(2):773-825. doi:10.1002/cphy.c150013[4]
  5. Ekmekcioglu C. Melatonin receptors in humans: biological role and clinical relevance. Biomed Pharmacother Biomedecine Pharmacother. 2006;60(3):97-108. doi:10.1016/j.biopha.2006.01.002[5]

Interested in nutrition? NUNM has several nutrition programs to choose from, including an online masters in nutrition, on-campus masters, a 3 year accelerated bachelor to master and a stand alone bachelor programs. Sign up and request more information to learn more about your options!