Intermittent fasting has gained popularity as a potentially effective approach to health and wellness, characterised by periods of voluntary abstinence from food and drink. However, its benefits and effectiveness remain a topic of ongoing research and debate.

Types of Intermittent Fasting:

  • Time-Restricted Feeding (TRF): Involves eating within a specific time window each day. Common variations include 16/8 (fasting for 16 hours, eating during an 8-hour window) and 12/12.
  • Alternate-Day Fasting (ADF): This involves alternating between days of normal eating and days where either very little or no food is consumed. Some versions allow for a minimal intake (around 500 calories) on fasting days.
  • 5:2 Fasting: In this approach, you eat normally for five days of the week and restrict calories to about 500-600 on the other two, non-consecutive days.
  • Eat-Stop-Eat: This involves a 24-hour fast, once or twice a week.
  • Spontaneous Meal Skipping: Skipping meals when convenient, without the need to follow a structured fasting plan.


Mixed Findings on Health Benefits

While some studies have reported benefits such as weight loss or improved metabolic health, others have found limited or no advantages compared to traditional dieting methods. This variability in outcomes may partly stem from individual differences in genetic makeup and lifestyle factors.


The Role of Genetics in Intermittent Fasting

There is no clear genetic factor implicated in the response to intermittent fasting but some research suggests changes in expression of the FTO and circadian rhythm genes. More specifically, a study1 reported decrease in the FTO gene expression in overweight and obese participants following Ramadan fasting period. (Note: The FTO gene, often referred to as the “fat mass and obesity-associated gene,” plays a significant role in regulating body weight and fat mass. It’s associated with an increased risk of obesity. Variants of the FTO gene are known to influence energy balance, appetite, and food intake regulation).

Another study2 exploring the effects of fasting in more than 600 people reported changes in expression of circadian rhythm genes in response to fasting highlighting adipose tissue as more “responsive” to fasting than skin. (Note: The CLOCK gene is essential in regulating circadian rhythms, which are the physical, mental, and behavioural changes following a daily cycle. It’s closely linked to various metabolic processes in the body, including glucose and lipid metabolism. Variations in the CLOCK gene have been associated with obesity, weight gain, suggesting that disruptions in circadian rhythms can influence weight regulation).



Although we are unable to pinpoint specific genetic variations that would be involved in the weight loss response to intermittent fasting, there is a clear involvement of genetics, with the FTO and circadian rhythm genes potential candidates. While more research is needed to fully understand these connections, the potential for tailored dietary approaches based on individual genetic profiles is an interesting prospect for the future of nutritional science.