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Metabolic rate and intermittent fasting

Metabolic rate and intermittent fasting

J Strength Cond Mteabolic. Metabolic rate and intermittent fasting is the fasting method, rage which you fast for 16 hours and eat in the remaining eight hours of the day. Metrics details. Keto, carnivore, and paleo. Journal of Translational Medicine ISSN: Tipton KD, Rasmussen BB, Miller SL, Wolf SE, Owens-Stovall SK, Petrini BE, Wolfe RR. Metabolic rate and intermittent fasting


Metabolic Switching, Fasting, Ketosis, Neuroplasticity, Diet, Neurodegenerative Disease Mark Mattson

Metabolic rate and intermittent fasting -

Purpose: The aim of this study was to identify the effects of intermittent fasting IF on resting metabolic rate RMR and respiratory exchange ratio RER. Intermittent fasting restricts the time interval in which calories are consumed without restricting the total number of calories.

Methods: The study was conducted over two weeks. During the control week, participants consumed their normal diet ad libitum. In the experimental week, participants consumed a eucaloric diet but were restricted to an eight-hour feeding interval.

Fasting RMR, RER, blood glucose, body composition, and cholesterol levels were measured. Data were collected at the end of each week. Results: During fasting, the average feeding interval was 6. There were no significant differences between total calories consumed or macronutrient distribution.

A significant decrease in RMR was found There were no significant differences between other measures. Conclusion : Previous studies on IF are inconclusive and have either not tested RMR, showed no significant difference, or found a decrease in RMR. The direct effect on metabolic rate and clinical measures related to IF have not been determined.

However, in our modern environment with artificial lights, hour convenience stores, and DoorDash, we are persistently primed to eat. Rather than obeying our circadian cues, we are eating at all times of day.

Plenty of research , mainly in animal models but also some human trials, indicates that your body experiences numerous benefits from being in a fasted state, given its impact on cellular processes and function. In a fully fasted state, your metabolism switches its primary source of fuel from glucose to ketones, which triggers a host of cellular signaling to dampen cellular growth pathways and increase cellular repair and recycling mechanisms.

Repeated exposure to a fasted state induces cellular adaptations that include increased insulin sensitivity, antioxidant defenses, and mitochondrial function.

Given how much of chronic disease is driven by underlying insulin resistance and inflammation, it's plausible that fasting may help reduce diabetes, high cholesterol, hypertension, and obesity. And multiple short-term clinical studies provide evidence that intermittent fasting — specifically, time-restricted feeding — can improve markers of cardiometabolic health.

To date, the answer has remained murky due to the quality of the evidence, which often involves very small sample sizes, short intervention periods, varied study designs often lacking control groups , different fasting protocols, and participants of varying shapes and sizes.

The data on intermittent fasting and its impact on weight loss largely involves studies that employ the time-restricted eating methodology of intermittent fasting. A recent compilation of the evidence suggests that limiting your eating window might indeed help you shed a few pounds.

To tease out the independent impact of time restriction on weight loss, we need to evaluate a calorie-restricted diet combined with time-restricted eating, compared to time-restricted eating alone. The recent results of a yearlong study assessed this exact question: does time-restricted eating with calorie restriction produce greater effects on weight loss and metabolic risk factors in obese patients, as compared with daily calorie restriction alone?

To answer this question, the trial involved people ages 18 to 75 with BMI s between 28 and 45, notably excluding those who were actively participating in a weight-loss program or using medications that affect weight or calorie intake.

In order to confirm adherence to the diet a notorious challenge in diet studies , participants were encouraged to weigh foods and were required to keep a daily dietary log, photograph the food they ate, and note the times at which they ate with the use of a custom mobile app.

Half of the participants those in the time-restricted eating group were instructed to consume the prescribed calories within an eight-hour period, whereas the other half in the daily-calorie-restriction group consumed the prescribed calories without time restriction.

Resting energy expenditure was unchanged, but a significant decrease in respiratory ratio was observed in the TRF group.

Our results suggest that an intermittent fasting program in which all calories are consumed in an 8-h window each day, in conjunction with resistance training, could improve some health-related biomarkers, decrease fat mass, and maintain muscle mass in resistance-trained males.

Fasting, the voluntary abstinence from food intake for a specified period of time, is a well-known practice associated with many religious and spiritual traditions. In fact, this ascetic practice is referenced in the Old Testament, as well as other ancient texts such the Koran and the Mahabharata.

In humans, fasting is achieved by ingesting little to no food or caloric beverages for periods that typically range from 12 h to 3 weeks. Muslims, for example, fast from dawn until dusk during the month of Ramadan, while Christians, Jews, Buddhists, and Hindus traditionally fast on designated days or periods [ 1 ].

Starvation could also refer to some extreme forms of fasting, which can result in an impaired metabolic state and death. However, starvation typically implies chronic involuntary abstinence of food, which can lead to nutrient deficiencies and health impairment.

While a prolonged period of fasting is difficult to perform for the normal population, an intermittent fasting IF protocol has been shown to produce higher compliance [ 3 ].

The most studied of the above form of IF is Ramadan fasting: during the holy month of Ramadan, which varies according to the lunar calendar, Muslims abstain from eating or drinking from sunrise to sunset. The effects of Ramadan have been extensively investigated, not only on health outcomes [ 1 , 4 — 8 ], but also on exercise performance [ 9 — 16 ].

Moreover, in recent years a focus on other forms of IF, unrelated to religious practice, has emerged. A growing body of evidence suggests that, in general, IF could represent an useful tool for improving health in general population due to reports of improving blood lipids [ 17 — 20 ] and glycaemic control [ 3 ], reducing circulating insulin [ 21 ], decreasing blood pressure [ 1 , 21 — 23 ], decreasing inflammatory markers [ 7 ] and reducing fat mass even during relatively short durations 8—12 weeks [ 23 ].

These reported effects are probably mediated through changes in metabolic pathways and cellular processes such as stress resistance [ 24 ], lipolysis [ 3 , 17 , 25 — 27 ], and autophagy [ 28 , 29 ].

One particular form of IF which has gained great popularity through mainstream media is the so-called time-restricted feeding TRF. TRF allows subjects to consume ad libitum energy intake within a defined window of time from 3—4 h to 10—12 h , which means a fasting window of 12—21 h per day is employed.

A key point concerning the IF approach is that generally calorie intake is not controlled, but the feeding times are. In sports, IF is studied mainly in relationship with Ramadan period [ 9 — 16 ], whilst TRF has become very popular among fitness practitioners claiming supposed effects on maintenance of muscle mass and fat loss.

Very limited scientific information is available about TRF and athletes, and mixed results have been reported [ 22 , 30 , 31 ]. We demonstrated very recently [ 30 ] that TRF did not affect total body composition nor had negative effects on muscle cross-sectional area after 8 weeks in young previously-untrained men performing resistance training, despite a reported reduction in energy intake of ~ kcal per fasting day in the TRF group.

Thus the aim of the present study was to investigate the effects of an isoenergetic TRF protocol on body composition, athletic performance, and metabolic factors during resistance training in healthy resistance trained males.

We hypothesized that the TRF protocol would lead to greater fat loss and improvements in health-related biomarkers as compared to a typical eating schedule. Therefore, 34 subjects age The research staff conducting outcome assessments was unaware of the assignment of the subjects i.

a single blind design. Anthropometric baseline characteristics of subjects are shown in Table 1. All participants read and signed an informed consent document with the description of the testing procedures approved by the ethical committee of the Department of Biomedical Sciences, University of Padova, and conformed to standards for the use of human subjects in research as outlined in the current Declaration of Helsinki.

Dietary intake was measured by a validated 7-day food diary [ 32 — 34 ], which has been used in previous studies with athletes [ 35 ], and analysed by nutritional software Dietnext®, Caldogno, Vicenza, Italy. Subjects were instructed to maintain their habitual caloric intake, as measured during the preliminary week of the study Table 2.

and 8 p. ND group ingested their caloric intake as three meals consumed at 8 a. This meal timing was chosen to create a balanced distribution of the three meals during the feeding period in the TRF protocol, while the schedule for the ND group maintained a normal meal distribution breakfast in the morning, lunch at 1 p.

and dinner at 8 p. The specific calorie distribution was assigned by a nutritionist and was based on the reported daily intake of each subject. ND subjects were instructed to consume the entire breakfast meal between 8 a.

and 9 a. and 2 p. and 9 p. TRF subjects were instructed to consume the first meal between 1 p. and 5 p. No snacks between the meals were allowed except 20 g of whey proteins 30 min after each training session.

Every week, subjects were contacted by a dietician in order to check the adherence to the diet protocol. The dietician performed a structured interview about meal timing and composition to obtain this information. Training was standardized for both groups, and all subjects had at least 5 years of continuous resistance training experience prior to the study.

Training consisted of 3 weekly sessions performed on non-consecutive days for 8 weeks. All participants started the experimental procedures in the months of January or February The resistance training program consisted of 3 different weekly sessions i.

a split routine : session A bench press, incline dumbell fly, biceps curl , session B military press, leg press, leg extension, leg curl , and session C wide grip lat pulldown, reverse grip lat pulldown and tricep pressdown.

the inability to perform another repetition with correct execution with s of rest between sets and exercises [ 36 ]. The technique of training to muscular failure was chosen because it is one of the most common practices for body builders, and it was a familiar technique for the subjects.

As expected, the muscle action velocity varied between subjects due to their different anatomical leverage. Although there was slight variation of repetition cadence for each subject, the average duration of each repetition was approximately 1.

The research team directly supervised all routines to ensure proper performance of the routine. Each week, loads were adjusted to maintain the target repetition range with an effective load.

Training sessions were performed between and p. Subjects were not allowed to perform other exercises other than those included in the experimental protocol.

Body weight was measured to the nearest 0. Fat mass and fat-free mass were assessed by dual energy X-ray absorptiometry DXA QDR W, Hologic Inc. Muscle areas were calculated using the following anthropometric system.

We measured limb circumferences to the nearest 0. We also measured biceps, triceps, and thigh skinfolds to the nearest 1 mm using a Holtain caliper Holtain Ltd, UK. All measurements were taken by the same operator AP before and during the study according to standard procedures [ 38 , 39 ].

Muscle areas were then calculated using a previously [ 40 ] validated software Fitnext®, Caldogno, Vicenza, Italy.

Ventilatory measurements were made by standard open-circuit calorimetry max Encore 29 System, Vmax, Viasys Healthcare, Inc. The gas analysis system was used: Oxygen uptake and carbon dioxide output values were measured and used to calculate resting energy expenditure REE and respiratory ratio RR using the modified Weir equation [ 43 ].

After resting for 15 min, the data were collected for 30 min, and only the last 20 min were used to calculate the respiratory gas parameters [ 37 , 44 ]. All tests were performed in the morning between 6 and 8 a. while the subjects were supine. The room was dimly lit, quiet, and approximately 23 °C.

Subjects were asked to abstain from caffeine, alcohol consumption and from vigorous physical activity for 24 h prior to the measurement. All samples were analysed in the same analytical session for each test using the same reagent lot.

Before the analytical session, the serum samples were thawed overnight at 4 °C and then mixed. The inter-assay coefficient of variations CVs were 3. Insulin-like growth factor 1 IGF-1 was measured using the analyzer Liaison XL DiaSorin S.

A, Vercelli-Italy. This test is a sandwich immunoassay based on a chemiluminescent revelation, and the CV for IGF-1 was between 5.

Fasting total cholesterol, high-density lipoprotein cholesterol HDL-C , low-density lipoprotein cholesterol LDL-C , and triglycerides TG were measured by an enzymatic colorimetric method using a Modular D Roche Diagnostics, Basel, Switzerland.

The inter-assay CVs for total cholesterol, HDL-C, and triacylglycerol concentrations were 2. Glucose was measured in triplicate by the glucose oxidase method glucose analyzer, Beckman Instruments, Palo Alto, CA, USA , with a CV of 1. Leptin and adiponectin were measured by radioimmunoassay using commercially available kits Leptin: Mediadiagnost; Adiponectin: DRG Diagnostic ; insulin was measured with a chemiluminescent immunoassay Siemens Immulite Thyroid-stimulating hormone TSH , free thyroxine T4 , and free triiodothyronine T3 were measured by automated chemiluminescence methods ACS SE; Bayer, Milan, Italy.

Plasma testosterone was determined using Testosterone II Roche Diagnostics, Indianapolis, IN, USA performed on Modular Analytics E analyzer with electrochemiluminescent detection. One repetition maximum 1-RM for the leg press and the bench press exercises was measured on separate days.

Subjects executed a specific warm-up for each 1-RM test by performing 5 repetitions with a weight they could normally lift 10 times. Using procedures described elsewhere [ 45 ], the weight was gradually increased until failure occurred in both of the exercises tested.

The greatest load lifted was considered the 1-RM. Previously published ICCs for test—retest reliability for leg press and bench press 1-RM testing was 0. Results are presented as mean ± standard deviation.

The sample size was obtained assuming an interaction of a Root Mean Square Standardized Effect RMSSE of 0. An independent samples t test was used to test baseline differences between groups.

The two-way repeated-measures ordinary ANOVA was performed using time as the within-subject factor and diet as the between-subject factor in order to assess differences between groups over the course of the study.

Post-hoc analyses were performed using the Bonferroni test. In order to reduce the influence of within group variability a univariate test of significance ANCOVA was performed.

We fixed as depended variable the Δ pre-post for each group and the baseline values of the outcomes were adopted as covariate; IF vs ND were assumed as categorical predictors.

The same trend was observed for arm and thigh muscle cross-sectional area. Leg press maximal strength increased significantly, but no difference was present between treatments. Total testosterone and IGF-1 decreased significantly in TRF after 8 weeks while no significant differences were detected in ND.

Blood glucose and insulin levels decreased significantly only in TRF subjects and conformingly a significant improvement of HOMA-IR was detected. In the TRF group, adiponectin increased, leptin decreased but this was not significant when normalized for fat mass , and T3 decreased significantly compared to ND, without any significant changes in TSH.

No significant changes were detectable for lipids total cholesterol, HDL-c and LDL-c , except for a decrease of TG in TRF group. TNF-α and IL-1β were lower in TRF at the conclusion of the study as compared to ND. A significant decrease of respiratory ratio in TRF group was recorded Tables 3 , 4.

However, only a single study has reported its effect during a resistance training program aimed at achieving skeletal muscle growth [ 30 ]. Our data demonstrate that during a RT program, TRF was capable of maintaining muscle mass, reducing body fat, and reducing inflammation markers.

However, it also reduced anabolic hormones such testosterone and IGF A key point of the TRF approach utilized in the present study is that total daily calorie intake remained the same while the frequency of meals i. time between meals was altered. This is dissimilar to many other IF regimens.

There are a number of different IF protocols, most of which have the goal of reducing total energy intake. Additionally, unlike ADF and some other forms of IF, the regimen utilized in the present study employed the same schedule each day, consisting of 16 h fasting and 8 h feeding.

Although IF has received a great amount of attention in recent years, the majority of studies have investigated the effects of IF in overweight, obese or dyslipidemic subjects [ 19 — 21 , 47 — 50 ]. However, little is known about the effects of such nutritional regimens in athletes, and more specifically, in body builders or resistance-trained individuals.

The present study provides the first in-depth investigation of IF in this population of athletes. With the exception of reduced triglycerides, our results do not confirm previous research suggesting a positive effect of IF on blood lipid profiles [ 17 — 19 , 47 , 49 , 51 , 52 ], however, it has to be taken into account that our subjects were normolipemic athletes.

The magnitude of reduction in triglycerides was also smaller than is typically seen in individuals who have elevated concentrations prior to IF. As reported, a decrease of fat mass in individuals performing IF was observed.

Considering that the total amount of kilocalories and the nutrient distribution were not significantly different between the two groups Table 2 , the mechanism of greater fat loss in IF group cannot simply be explained by changes in the quantity or quality of diet, but rather by the different temporal meal distribution.

Many biological mechanisms have been advocated to explain these effects. Moreover, adiponectin acts in the brain to increase energy expenditure and cause weight loss [ 53 ].

It is notable that in the present study, the differences in adiponectin between groups remained even when normalized relative to body fat mass, whereas the significant decrease of leptin that might be considered a unfavorable factor for fat loss was no longer significant when normalized for fat mass.

Interestingly, although reductions in the anabolic hormones testosterone and IGF-1 were observed, this did not correspond to any deleterious body composition changes or compromises of muscular strength over the duration of the study. It has been previously reported that men performing caloric restriction have lower testosterone than those consuming non-restricted Western diets [ 56 ], however, the present experiment did not restrict calories in the IF group.

Also, the reduction of IGF-1 in the TRF group deserves some discussion. A previous study by Bohulel et al. Even though it is plausible that IF mimics caloric restriction through common pathways e.

It is possible that the increase of adiponectin and the decrease of leptin could influence the IGF-1 concentration, even though it is unclear to what extent changes in adipokines impact circulating IGF-1 levels following weight loss [ 59 ].

Previous studies have reported mixed results concerning the ability to maintain lean body mass during IF, but the vast majority of these studies imposed calorie restriction and did not utilize exercise interventions [ 22 ].

In our study, the nutrient timing related to training session was different between the two groups, and this could affect the anabolic response of the subjects [ 61 ] even though these effects are still unclear [ 62 ].

However, we did not find any significant differences between groups in fat-free mass, indicating that the influence of nutrient timing may be negligible when the overall content of the diet is similar. There is an increasing amount of data suggesting that IF could potentially be a feasible nutritional scheme to combat certain diseases.

In the present study, both blood glucose and insulin concentrations decreased in the IF group. The potential of IF to modulate blood glucose and insulin concentrations has previously been discussed, but primarily in the context of overweight and obese individuals [ 3 ]. The concurrent increase in adiponectin and decrease in insulin may be related to modulation of insulin sensitivity, as adiponectin concentrations have been positively correlated with insulin sensitivity [ 21 , 50 , 63 , 64 ].

Moreover, related to the well-known anti-inflammatory effect of adiponectin, it is possible that the reduction of inflammatory markers is related to the improvement of insulin sensitivity.

Inflammation plays an pivotal role in insulin resistance development through different cytokines that influence numerous molecular pathways.

Moreover IL-6 could decrease insulin sensitivity in skeletal muscle by inducing toll-like receptor-4 TLR-4 gene expression through STAT3 activator of transcription 3 activation.

Modulation of some of these inflammatory markers by IF was seen in the present study: TNF-α and IL-1β were lower in the TRF group than ND at the conclusion of the study, while IL-6 appeared to decrease in the TRF group, but was not significantly different from ND.

Previous information on the impact of IF on inflammatory markers is limited, but a previous investigation by Halberg et al. Although a reduction in T3 was observed in the IF group, no changes in TSH or resting energy expenditure were observed. The observed reduction in RR in the TRF group indicates a very small shift towards reliance on fatty acids for fuel at rest, although a significant statistical interaction for RR was not present.

Fasting RR has been previously reported to be a predictor of substantial future weight gain in non-obese men, with individuals who have higher fasting RR being more likely to gain weight [ 67 ].

Interestingly, it was reported by Seidell et al. Based on the present study, a modified IF protocol i. TRF could be feasible for strength athletes without negatively affecting strength and muscle mass.

Caloric restriction in rodents has been reported to decrease testosterone and IGF-1 even though human data on long-term severe caloric restriction does not demonstrate a decrease in IGF-1 levels, but instead an increased serum insulin-like growth factor binding protein 1 IGFBP-1 concentration [ 60 , 68 ].

However, no data are available for most forms of IF. In addition to altering IGF-1, fasting can promote autophagy [ 28 ], which is important for optimal muscle health [ 70 ]. Additionally, there is a possibility that the different eating patterns of the groups in the present study impacted the relative contributions of different hypertrophic pathways in each group.

Some limitations of the present study should be taken into account. On this point, there is not a consensus among researchers. The beneficial effects of pre-exercise essential amino acid-carbohydrate supplement have been suggested [ 61 ], but the same group found that ingesting 20 g of whey protein either before or 1 h after 10 sets of leg extension resulted in similar rates of AA uptake [ 62 ].

Additionally, other studies have reported no benefit with pre-exercise AA feeding [ 71 , 72 ]. Another limitation of the present study is that the energy and macronutrient composition of the diet was based on interview, and this approach has known weaknesses.

Because of the limitations of this method, it is possible that differences in energy or nutrient intake between groups could have existed and played a role in the observed outcomes. In conclusion, our results suggest that the modified IF employed in this study: TRF with 16 h of fasting and 8 h of feeding, could be beneficial in resistance trained individuals to improve health-related biomarkers, decrease fat mass, and at least maintain muscle mass.

This kind of regimen could be adopted by athletes during maintenance phases of training in which the goal is to maintain muscle mass while reducing fat mass. Additional studies are needed to confirm our results and to investigate the long-term effects of IF and periods after IF cessation.

Trepanowski JF, Bloomer RJ. The impact of religious fasting on human health. Nutr J. Article PubMed PubMed Central Google Scholar. Longo VD, Mattson MP.

In fact, anc fasting, a dietary intermitfent that cycles between periods fadting fasting aand Metabolic rate and intermittent fasting, is often promoted as a miracle diet. People commonly believe Metabolic rate and intermittent fasting skipping breakfast leads to Glutamine for muscle building hunger, cravings, and weight gain. Some studies even suggest that people who lose weight over the long term tend to eat breakfast 2. Breakfast is beneficial for some people, while others can skip it without any negative consequences. Many people believe that eating more meals increases your metabolic rate, causing your body to burn more calories overall. Your body indeed expends some calories digesting meals. Intermittent Mtabolic is a trendy topic Metabolic rate and intermittent fasting arises repeatedly in my clinic these days. I get it: Metabllic the time period when you eat, but within that time window eat as you normally would. No calorie counting. No food restrictions. Simple and flexible. In an on-the-go world, intermittent fasting has come into vogue as a potential pathway toward sustainable weight loss.

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