What is Intermittent Fasting?
Intermittent fasting (IF) is not a diet, but rather an eating pattern that involves alternating periods of eating and fasting. The idea is to limit your eating to a specific window of time each day.
Different Types of IF:
The most popular version of IF is called 16:8. This involves eating during an 8-hour window, and fasting for the remaining 16 hours. For example, finish dinner at 8 pm and don’t eat again until noon the next day.
Other forms of IF involve alternate-day fasting or eating normally for five days of the week and severely restricting calorie intake on the remaining two days. These can be dangerous without medical supervision.
How Does It Work?
When you eat food, your body breaks it down into energy. During the fasting period, your body starts using stored energy, like fat, for fuel. This has shown potential benefits in the areas of weight loss, digestion, and overall health. However, IF also has potential concerns and is not a suitable eating pattern for everyone.
IF may help you lose weight or maintain a healthy weight by reducing calorie intake.
IF may improve insulin sensitivity and lower the risk of type 2 diabetes.
IF may improve lipid profiles and blood pressure.
Some people find that fasting helps them feel more energetic and focused.
Giving your body a break from constant eating can improve digestion and reduce bloating.
Some studies suggest it could reduce inflammation and improve heart health markers.
Animal studies show potential benefits to brain health, cancer prevention, and anti-aging.
Note: Keep in mind that research is still in its early stages. Many of the studies were small, short-term or conducted in animals. Many questions have yet to be answered in human studies.
Nutritional deficiencies: IF can restrict the intake of essential nutrients, including vitamins, minerals, and micronutrients.
Disordered eating patterns: IF may trigger obsessive thoughts about food, a preoccupation with meal timing, and an unhealthy focus on weight loss.
Blood sugar imbalances: Fasting for prolonged periods may cause fluctuations in blood sugar levels, leading to hypoglycemia (low blood sugar) or hyperglycemia (high blood sugar).
Increased risk of overeating or binge eating: Restricting food intake for prolonged periods can trigger excessive hunger and cravings, potentially leading to overeating or binge eating behaviors during eating windows.
Psychological effects: Some individuals may experience mood swings, irritability, difficulty concentrating, or feelings of deprivation during fasting periods.
RENEW Program Stance:
At this time, there is not enough evidence to recommend intermittent fasting.
Restricted eating times could pose challenges to people meeting their nutrition goals. There is also some concern about whether this eating pattern might enhance cravings or stress around food. IF is not suitable for individuals who struggle with emotional eating, binge eating, or an eating disorder.
However, if you choose to pursue this approach, consult your health care provider and your coach about how to continue meeting your nutrition goals. Remember that maintaining a balanced diet and focusing on nutrient-dense foods during eating periods is crucial for overall health.
Harvard T.H. Chan School of Public Health. (2022, May 17). Diet review: Intermittent fasting for weight loss. The Nutrition Source. https://www.hsph.harvard.edu/nutritionsource/healthyweight/diet-reviews/intermittent-fasting/
Harvie, M., & Howell, A. (2017). Potential Benefits and Harms of Intermittent Energy Restriction and Intermittent Fasting Amongst Obese, Overweight and Normal Weight Subjects—A Narrative Review of Human and Animal Evidence. Behavioral Sciences, 7(4), 4. https://doi.org/10.3390/bs7010004
Song, D. K., & Kim, Y. W. (2023). Beneficial effects of intermittent fasting: a narrative review. Journal of Yeungnam medical science, 40(1), 4–11. https://doi.org/10.12701/jyms.2022.00010
Some key points to understand about intermittent fasting