The short-term effects of intermittent fasting on fat metabolism


Editor: David L. Joffe, BSPharm, CDE, FACA

Author: Destiny Reed, PharmD. Candidate, Florida A&M College of Pharmacy and Pharmaceutical Sciences

Intermittent fasting has been shown to increase fat metabolism in the early morning hours in healthy, lean adults.

Intermittent fasting has become a very common eating habit in recent years. Common types of intermittent fasting include the 16/8 method, (16 hours of fasting and 8 hours for food consumption) and the 5: 2 diet, where calorie consumption is restricted only two days per week. Intermittent fasting is associated with reduced total calorie intake and weight loss and is believed to extend low insulin intervals and increase ketogenesis, among other things. It was hypothesized that adipose tissue mobilization could be increased by prolonging low nocturnal insulin levels until morning fasting: This open, crossover study aimed to determine whether early morning fasting could increase blood metabolism. adipose tissue.

The primary outcome measure measured in this study was the mobilization of adipose tissue. Mobilization of adipose tissue was calculated by obtaining the AUC of -hydroxybutyrate and free fatty acids over 6 hours. Secondary outcomes measured included mobilization of intestinal peptides (concentrations of GLP-1 and YY peptide and ghrelin AUC) and the degree of appetite suppression and induction of satiety over 6 hours. The degrees of appetite suppression and satiety induction were measured using visual analog scales.

Participants in this study performed three 6-hour morning sessions after an overnight fast. Each session took place 1 to 3 weeks apart. The participant would continue to fast, consume a 500 kcal Mediterranean-style breakfast or a 500 kcal no-carbohydrate breakfast in random order. Basic measurements were taken at the start of each visit, including fasting length, FBG, fasting insulin, insulin resistance, and -hydroxybutyrate. Plasma glucose, insulin, and visual analog scale readings were taken every 30 minutes for the first 120 minutes of the session, and then every 60 minutes until the end of the session. The concentrations of -hydroxybutyrate were measured by a colorimetric assay every hour.

Participants had to be between 18 and 45 years old and have a BMI of 18 to 25 kg / m2 to be eligible for this study. Additionally, participants were excluded from the trial if they had an uncontrolled thyroid disorder, type 1 or 2 diabetes mellitus, or a BMI> 25 kg / m2. Linear mixed models were used to analyze the data collected during the study. AUCs were calculated using the trapezoidal rule for all measured data.

Ten people participated in this study, of which 70% were women. The mean age of the individuals in the study was 28.6 years, with an average BMI of 22.9 kg / m2. Linear regression showed a positive correlation between the duration of the fast and the adjusted AUC of -hydroxybutyrate (beta = 0.416, p = 0.018). A negative correlation was demonstrated between insulin resistance and AUC of β-hydroxybutyrate (beta = -0.398, p = 0.024). After adjusting for insulin resistance and fasting duration, the measured AUC of β-hydroxybutyrate was higher after the fasting sessions than the carbohydrate-free and Mediterranean sessions (p = 0.021 and p = 0.008, respectively).

There was no significant difference in the measurement of the AUC of β-hydroxybutyrate between the non-carbohydrate and Mediterranean-type sessions. Glucose AUC was similar for all three sessions. The insulin AUC was significantly lower in the fasting session than in the Mediterranean session (p

This study showed that intermittent early morning fasting could achieve lower insulin levels and greater body fat mobilization than eating a no-carb, Mediterranean-style breakfast in healthy adults. Overall, the no-carb and Mediterranean-style breakfasts were similar, although more prolonged hunger suppression was associated with the no-carb breakfast. While this study confirmed the prolongation of low insulin levels and the mobilization of fat stores for short-term intermittent fasting, more research will be needed to assess the effects of morning fasting on long-term metabolic outcomes.

Practice beads:

  • Greater adipose tissue mobilization and lower insulin levels have been achieved with early morning fasting in lean and healthy individuals compared to a low-carb or Mediterranean breakfast.
  • Intermittent fasting resulted in the lowest hunger suppression followed by Mediterranean breakfast.
  • Overall fat tissue mobilization and insulin levels were similar between the no-carb and Mediterranean-style breakfasts.

56th EASD Annual Meeting of the European Association for the Study of Diabetes. Diabetologia 63, 1-485 (2020).

“Metabolic Effects of Morning Fasting 8/16 – Full Text View – Clinicaltrials.Gov”. Clinical Trials.Gov, 2020,

Destiny Reed, PharmD. Candidate, Florida A&M College of Pharmacy and Pharmaceutical Sciences


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