Recent study that fast-mimicking bar successfully prolonged fasting state in subjects


A recent study found that a bar, called Fast Bar from L-Nutra, successfully prolonged ketogenesis during a 15-hour overnight fast and mitigated fasting-associated side effects.


Image courtesy of L-Nutra

A recent study1 found that a bar, called Fast Bar from L-Nutra (Plano, TX), successfully prolonged ketogenesis during a 15-hour overnight fast and mitigated fasting-associated side effects. Intermittent fasting (IF), which combines periods of eating with periods of fasting, is becoming a popular practice used to lose weight and improve metabolic health.

“These eating or fasting ‘windows,’ as they’re called, help your body to burn fat for fuel while initiating the intracellular (meaning within the cell) clean-up and recycling process known as autophagy. Water, coffee, tea, and other non-calorific beverages are typically allowed (and recommended) during these fasts,” explains Valter Longo, PhD, creator of the Fast Mimicking Diet (FMD). “Since most people aren’t capable of eating during sleep, everybody practices intermittent fasting to some extent. The shortest window of IF begins with a 12-hour fasting window and can be as long as 20 hours or more. Any fasting of less than 2 days is considered intermittent fasting.”

FMD is made up of plant-based and scientifically-tested ingredients low in carbohydrates and proteins, that when consumed prolong the body’s fasting state because it does not recognize that one is eating. Fast Bar was clinically tested as part of FMD.

“Essentially, FMD works to trick the body’s nutrient sensors to disregard the hormone signal that you’ve eaten. The cells notice the decrease in this signal and enter a rejuvenating fasting state,” says William Hsu, MD, chief medical officer for L-Nutra, and one of the study’s researchers. “Fast Bar has been designed to provide your body with a carefully balanced ratio of macro- and micro-nutrients for satiety. In the randomized, controlled study of 105 adults who completed a 15-hour overnight fast, we compared glucose and ketone results every hour for 4 hours in a Fast Bar group, breakfast group and water-fast group, and found that the Fast Bar did not break the fast, thus allowing extension of the intermittent fasting window.”

The bar therefore allows consumers to eat during their fast, reducing hunger, while maintaining the fast. Fast Bar could therefore be eaten in the morning for nourishment while also extending the fast begun during sleep, as a snack during the day to curb hunger, or even as a late night snack that does not induce high blood glucose.

“Fast Bar offers nourishing ingredients with almonds, macadamias and pecans being the top 3 ingredients. It provides plant-based protein, good fats from nuts, and is rich in fiber and made without soy or diary,” explains Hsu. “Fast Bar has 7g of dietary fiber—premium nuts being the main source. A healthy nutrition bar shouldn’t have any trans fats. It should however offer a good amount of healthy, monounsaturated fats often found in nuts. Fast Bar has no trans fats and 9g of healthy monounsaturated fat.”

Fast Bar is not a meal replacement, and L-Nutra recommends that it be eaten only once a day in addition to following a healthy, balanced diet that consists of other regular meals during the day. For a more regimented, safe fasting experience with consistent results, L-Nutra also offers a five-day program called ProLon.


  1. Huang AW et al. “An Intermittent Fasting Mimicking Nutrition Bar Extends Physiologic Ketosis in Time Restricted Eating: A Randomized, Controlled, Parallel-Arm Study.” Nutrients, vol. 13, no. 5 (2021): 1523
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