The Effects of a High Carbohydrate vs. High Fat Pre-Fast Meal on Incretin Hormone Secretion: A Randomized Crossover Study

Chronic illness such as strokes, heart disease and diabetes all rank among the leading causes of death in the United States. Recently, fasting has gained popularity as a means of preventing and treating chronic illness. PURPOSE: Fasting produces multiple beneficial physiological responses that have been shown to aid in chronic disease prevention, one of which is observed in relation to incretin hormones such as glucose-dependent insulin tropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1). These incretin hormones are released by the gut to augment the secretion of insulin to regulate postprandial glucose levels. During a fast, the decrease in incretin hormones, and resultant insulin levels can aid the body to regain insulin sensitivity. This can lead to more effective blood glucose management and chronic illness prevention. The purpose of the study was to determine the impact of an acute 24-hour fast started with either a high fat (HF) or high carbohydrate (HC) meal on plasma GIP and GLP-1. METHODS: Subjects were over the age of 55, had a BMI equal to or greater than 27, and had no diagnosed metabolic disorders or some other disqualifying medical issues. Using a randomized crossover design, each participant performed two 24-hour fasts. One fast beginning with a high carbohydrate meal and the other a high fat meal, both of equal calories. Venous blood draws were taken at 0, 1, 24, and 48 hours. RESULTS: GIP and GLP-1 (P \u3c 0.001) were both elevated 1 hour after consuming the pre-fast meal in both conditions. In addition, both GIP (P = 0.0122) and GLP-1 (P = 0.0068) were higher in the high fat condition compared to the high carbohydrate condition at 1 hour. There were no significant differences between conditions for either GIP or GLP-1 at any other time point. CONCLUSION: As expected, both incretin hormones spiked postprandially. We did find that GIP and GLP-1 levels were significantly higher at 1-hour postprandial for the HF meal compared to the HC meal. This could give evidence to show how macronutrient levels can affect incretin secretion and alter sensitivity to insulin. However, the impact of the pre-fast meal on GLP-1 and GIP did not persist throughout the fast

The Effects of a High-Carbohydrate Versus a High-Fat Shake on Biomarkers of Metabolism and Glycemic Control When Used to Interrupt a 38-Hour Fast: A Randomized Crossover Study

As the link between metabolic health and chronic diseases have come into focus, it has highlighted the need to establish methods for improving metabolic flexibility. The ability to efficiently switch metabolic fuels from glucose to fatty acid-derived ketones is an indication of good metabolic health. Regular fasting allows the body to make the metabolic switch to ketones more often, which is commonly identified through the measurement of the ketone beta-hydroxybutyrate (BHB). Measuring both BHB and glucose levels can provide information about the body’s response to various foods, fasting regimens, or other metabolic stressors, and give valuable insights to measuring a metabolic switch. PURPOSE: The primary aim of this study was to determine the impact of various fast-interrupting shakes on markers of glycemic control including glucose, β-hydroxybutyrate (BHB), insulin, glucagon, GLP-1, and GIP. METHODS: Twenty-seven adults (12 female, 15 male) completed all three conditions of this study. One condition consisted of a 38-hour water-only fast, and the other two conditions were similar but the fasts were interrupted at 24 hours by either a high carbohydrate/low fat (HC/LF) or a low carbohydrate/high fat (LC/HF) shake. RESULTS: The water only fast resulted in 135.3% more BHB compared to the HC/LF condition (t = 7.77, p\u3c 0.0001) and 69.6% more compared to the LC/HF condition (t = 5.12, p \u3c 0.0001). Conversely, the LC/HF condition exhibited a 38.8% higher BHB level than the HC/LF condition (t = 2.70, p = 0.0086). Additionally, the area under the curve (AUC) for glucose was 14.2% higher in the HC/LF condition than in the water condition (t = 6.23, p \u3c 0.0001) and 6.9% higher compared to the LC/HF condition (t = 3.14, p =0.0024), with the LC/HF condition yielding 7.8% more glucose than the water condition (t = 3.21, p = 0.0020). At the 25-hour mark, insulin was significantly elevated in the HC/LF condition compared to the LC/HF condition (F = 3.84, p = 0.0002) and compared to the water condition (F = 7.00, p \u3c 0.0001). Furthermore, insulin was increased in the LC/HF condition compared to the water condition at 25 hours (F = 3.19, p = 0.0016). CONCLUSION: While a LC/HF shake does not mimic a fast completely, it does preserve some of the metabolic changes including elevated BHB and glucagon, and decreased glucose and insulin compared to a HC/LF shake

The Effects of Initiating a 24-hour Fast with a Low Versus a High Carbohydrate Shake on pancreatic hormones in the Elderly: A Randomized Crossover Study

Begin PURPOSE: The aim of this study is to understand how the macronutrient composition of the fast-initiating meal influences glucose regulating hormones during, and 24-hours after a 24-hour fast in older, sedentary, and abdominally obese adults. Understanding these outcomes will inform fasting protocols such as time restricted eating and alternate day fasting, which offer potential long-term health benefits. METHODS: We had 16 participants (7 male, 9 female). Each participant completed two 24-hour fasts (water only). In random order, one fast began with a high carb/low fat (HC/LF) shake and the other with a low carbohydrate/high fat shake (LC/HF) (equal calorie, volume and fiber). Venous blood draws were taken at hours 0, 1, 24, and 48. Participants fasted for 24 hours under free living conditions. RESULTS: There was a significant condition by time interaction for insulin (F = 4.08, P \u3c 0.01), amylin (F = 3.34, P = 0.02) and glucagon (F = 7.93, P \u3c 0.01). One hour after the consumption of the pre-fast shakes the LC/HF shake resulted in lower insulin (P = 0.02), amylin (P = 0.01) and higher glucagon (P = 0.05) compared to the HC/LF shake. However, there was no difference between conditions for insulin, glucagon or amylin at 0, 24 or 48 hours. CONCLUSION: Starting a fast with a LC/HF meal reduces the insulin response and increases glucagon which is beneficial for the switching of metabolic fuels from glucose to fat oxidation. However, this difference between conditions in hormone concentrations was not sustained over the course of the fast, as values for both glucagon, amylin and insulin were similar between conditions by 24 hours

The Effects of Alternate Day Modified Fasting on Diet and Weight Loss: A Pilot Study

Alternate day fasting has been shown to be an effective strategy for weight loss and improving metabolic health but adherence is challenging. Alternate day modified fasting (ADMF) is an alternative approach that allows for a meal (~25% of calories) to be consumed on the fast day to help make the fasting protocol more sustainable. PURPOSE: The objective of this study was to examine the impact of a 14-day alternate day modified fast on energy intake, macronutrient composition and body composition. METHODS: Forty two participants (24 male/18 female) completed 3 days of baseline testing followed by a 14-day treatment period where they followed a modified alternate day fasting regimen that consisted of fasting days alternated with normal eating days. On the fasting days the participants consumed 25% of their daily caloric requirements in one meal. Diet was assessed using the automated self-administered 24-hour recall. There were 2 days assessed at baseline and 4 random non-consecutive days assessed during the intervention period (2 fasting and 2 non-fasting days in the ADMF condition). Body weight and composition were assessed at the beginning and end of the intervention period. Body composition was assessed by DXA. RESULTS: There was a significant period by condition interaction for energy intake (F = 105.4, P \u3c 0.01), grams of protein (F = 51.1, P \u3c 0.01), fat (F = 121.0, P \u3c 0.01) and carbohydrate (F = 63.8, P \u3c 0.01). Average daily energy intake (-620 ± 51 kcal, P \u3c 0.01) and consumption of protein (-20 ± 3 g, P \u3c 0.01), fat (-27 ± 3 g, P \u3c 0.01) and carbohydrate (-77 ± 6 g, P \u3c 0.01) went down from baseline in ADMF, and all but carbohydrate (P = 0.16) were significantly different from control. For ADMF, all dietary variables were significantly lower on the fast days compared to the non-fast days (Ps \u3c 0.01). There was no significant difference between conditions for weight (F = 0.1, P = 0.83) or total body fat (F = 0.1 and P = 0.77). CONCLUSION: These findings indicate that the practice of alternate day modified fasting is an effective strategy for reducing caloric consumption. However, 14 days may not be long enough for this level of energy restriction to manifest changes in body weight and fat

“Cheating” In a Fast by Exercising After a Snack

As the prevalence of chronic diseases has increased, research has emerged supporting the utility of intermittent fasting in managing certain health conditions. Despite potential benefits, adhering to a fasting regimen can be difficult. PURPOSE: The purpose of this study was twofold. The first purpose was to describe how consuming a modest snack prior to exercise influences plasma glucose, beta-hydroxybutyrate and hunger in reference to fasting with and without exercise. The second purpose was to examine how exercising in a fasted state influences plasma glucose, beta-hydroxybutyrate and hunger. METHODS: A randomized crossover design with counterbalanced treatment conditions was used to compare the influence of fasting alone (control), fasting with exercise (exercise), and fasting with the addition of a snack immediately prior to exercise (snack/exercise). The effects of these interventions on beta-hydroxybutyrate levels, blood glucose, hunger, and mood were assessed. RESULTS: BHB was significantly higher in the exercise condition than control starting at 24 hrs to the end of the study (p \u3c 0.05). BHB levels between control and snack/exercise conditions were not different. Immediately after participants had exercised, blood glucose levels were higher in both the exercise and snack/exercise conditions than control (p \u3c 0.001). With the exception of one time point, there were no additional differences. In the exercise and snack/exercise conditions, hunger was significantly lower than control right after exercise (p = .0043 and p = .0003, respectively). Hunger was not different between the exercise and snack/exercise conditions at any time point. Mood was not different between conditions. CONCLUSIONS: Exercising after modest caloric intake produces BHB and glucose levels that are similar to fasting alone. Exercising without a snack briefly interrupts the fast but elevates BHB production starting around three hours after the exercise bout. Finally, mood was not different between any conditions and calls into question the assumption that a snack/exercise fasting protocol is in fact easier to adhere to

The Effects of Exercise on Inflammatory Biomarkers over a 36-h Fast

Postprandial and diet-induced chronic inflammation has become a popular point of discussion over recent years in lifestyle medicine as studies have uncovered the effects that various inflammation markers have on chronic diseases including heart disease, diabetes mellitus, and arthritis. Interventions to help lower inflammation could help promote longevity and decrease risk of chronic diseases. PURPOSE: While previous research has shown various effects of fasting on inflammatory biomarkers, this study assessed the impact of an acute 36h fast with or without exercise at the beginning on inflammatory biomarkers (IL-6, C-peptide, GIP, MCP-1, and TNF-alpha). METHODS: Twenty healthy subjects (11 male, 9 female) completed two 36h fasts, with one protocol requiring the subject to complete a treadmill exercise session prior to fasting. Venipuncture was performed every 12 h and samples were later analyzed for inflammatory biomarkers. RESULTS: GIP decreased over the first 12 hours of the fast (pCONCLUSION: Acute fasting reduces GIP, MCP-1 and C-peptide but most of the changes occurred during the first 24 hours of the fast. When exercise was combined with the 36h fast, levels of both C-Peptide and MCP-1 are significantly altered

The Effects of Exercise on Inflammatory Biomarkers over a 36-h Fast

Postprandial and diet-induced chronic inflammation has become a popular point of discussion over recent years in lifestyle medicine as studies have uncovered the effects that various inflammation markers have on chronic diseases including heart disease, diabetes mellitus, and arthritis. Interventions to help lower inflammation could help promote longevity and decrease risk of chronic diseases. PURPOSE: While previous research has shown various effects of fasting on inflammatory biomarkers, this study assessed the impact of an acute 36h fast with or without exercise at the beginning on inflammatory biomarkers (IL-6, C-peptide, GIP, MCP-1, and TNF-alpha). METHODS: Twenty healthy subjects (11 male, 9 female) completed two 36h fasts, with one protocol requiring the subject to complete a treadmill exercise session prior to fasting. Venipuncture was performed every 12 h and samples were later analyzed for inflammatory biomarkers. RESULTS: GIP decreased over the first 12 hours of the fast (pCONCLUSION: Acute fasting reduces GIP, MCP-1 and C-peptide but most of the changes occurred during the first 24 hours of the fast. When exercise was combined with the 36h fast, levels of both C-Peptide and MCP-1 are significantly altered

The Effects of Exercise on Hunger and Satiety Hormone Concentrations Over a 36-Hour Fast: A Randomized Crossover Study

Background: Feelings of hunger and satiation are known to be influenced physiologically through hormone secretion. Ghrelin (GH) is known as the primary “hunger” hormone, and GLP-1, PP, PYY, and C-Peptide (CP) are hormones known to signal feelings of satiety. The aim of this study was to assess hunger and satiety hormone production during a prolonged fast, and to evaluate how an initial bout of exercise influences this secretion. Subjective feelings of mood and hunger were also assessed throughout. Methods: In this crossover study, 20 adult subjects (11 Male, 9 Female) completed two 36-hour fasts, with one protocol requiring the subject to complete an intense treadmill exercise session at the beginning of the fast. Hunger and satiety hormone levels were assessed via venous blood samples taken every 12 hours. Subjective mood and hunger ratings were also recorded via an online survey every two hours. Results: Compared with fasting only conditions, exercise conditions suppressed ghrelin secretion during the first 24 of the 36 hours of the fast (P = 0.01). Additionally, compared to fasting only conditions, hormone secretions of GLP-1 (P = .04) and C-peptide (P = .035) were significantly increased when compared to the fasting alone intervention between the initial measurements and at 12 and 24 hours after initiating the fast. However, subjective feelings of hunger and stomach discomfort did not differ between conditions. Conclusions: Completing a bout of aerobic exercise at the beginning of a 36-hour fast results in significant decrease in ghrelin and significant increases in satiety hormone secretions while not making a significant impact on subjective ratings of hunger and stomach discomfort. Concentrations of hunger and satiety hormones provide evidence that an individual should feel less desire to consume food during a prolonged fast if they initiate that fast with a bout of aerobic exercise

The Effects of Exercise on Appetite-Regulating Hormone Concentrations over a 36-h Fast in Healthy Young Adults: A Randomized Crossover Study

Hunger and satiety are controlled by several physiological mechanisms, including pancreatic and gastrointestinal hormones. While the influence of exercise and fasting have been described individually, in relation to these hormones, there is a paucity of work showing the effects of the two modalities (fasting and exercise) combined. Twenty healthy adults (11 males, 9 females) completed both conditions of this study, each consisting of a 36-h water-only fast. One of the fasts began with treadmill exercise, and the differences between the conditions on various appetite hormones were measured every 12 h. The difference in the area under the curve between conditions for ghrelin was 211.8 ± 73.1 pg/mL (F = 8.40, p p < 0.0422). No significant differences were noted for areas under the curve between conditions for leptin, PP, PYY, insulin, or GIP. Initiating a fast with exercise lowers ghrelin concentrations and elevates GLP-1 concentrations. Given that ghrelin elicits feelings of hunger and GLP-1 signals feelings of satiety, adding exercise to the beginning of a fast may reduce some of the biological drive of hunger, which could make fasting more tolerable, leading to better adherence and more significant health outcomes