Fasting and metabolism -
The hike seen in the metabolites associated with this process means that the mitochondria, the fabled powerhouses of the cell, are thrust into overdrive. Another surprise finding was an increase in levels of purine and pyrimidine, which scientists had not yet linked to fasting.
These chemicals are a sign of increased protein synthesis and gene expression. This suggests that fasting causes cells to switch up the type and quantity of proteins that they need to function. Higher levels of purine and pyrimidine are clues that the body might be increasing levels of certain antioxidants.
Indeed, the researchers noted substantial increases in certain antioxidants, including ergothioneine and carnosine. In an earlier study , the same team of researchers showed that, as we age, a number of metabolites decline.
These metabolites include leucine, isoleucine, and ophthalmic acid. In their latest study, they showed that fasting boosted these three metabolites. They explain that this might help explain how fasting extends lifespan in rats. In all four subjects, the researchers identified 44 metabolites that increased during fasting, some of which increased fold.
Of these 44, scientists had linked just 14 to fasting before. This result suggests the possibility of a rejuvenating effect by fasting, which was not known until now.
The scientists believe that a hike in antioxidants might be a survival response; during starvation, our bodies can experience high levels of oxidative stress. By producing antioxidants, it might help avoid some of the potential damage caused by free radicals.
Next, they want to replicate the results in a larger sample. They also want to identify possible ways of harnessing the beneficial effects of fasting and find out whether they can trigger the effects of caloric restriction without having to restrict caloric intake.
Although it will be some time before we can reap the benefits of fasting without the effort, the current findings provide further evidence of the health benefits of fasting. A new clinical trial shows that time-restricted eating, also known as intermittent fasting, helps relieve symptoms of metabolic syndrome.
Scientists conducted a small study of the day fasting practice of Ramadan and found evidence of significant metabolic benefits. A recently published small-scale study investigates whether intermittent fasting might be a useful intervention for individuals with type 2 diabetes.
The food we eat is broken down by enzymes in our gut and eventually ends up as molecules in our bloodstream. Carbohydrates, particularly sugars and refined grains think white flours and rice , are quickly broken down into sugar, which our cells use for energy.
If our cells don't use it all, we store it in our fat cells as, well, fat. But sugar can only enter our cells with insulin, a hormone made in the pancreas.
Insulin brings sugar into the fat cells and keeps it there. Between meals, as long as we don't snack, our insulin levels will go down and our fat cells can then release their stored sugar, to be used as energy. We lose weight if we let our insulin levels go down.
The entire idea of IF is to allow the insulin levels to go down far enough and for long enough that we burn off our fat. Initial human studies that compared fasting every other day to eating less every day showed that both worked about equally for weight loss, though people struggled with the fasting days.
So, it's very reasonable to choose a reduced calorie plant-based, Mediterranean-style diet. But research suggests that not all IF approaches are the same, and some IF diets are indeed effective and sustainable, especially when combined with a nutritious plant-based diet. Our metabolism has adapted to daytime food, nighttime sleep.
Nighttime eating is well associated with a higher risk of obesity, as well as diabetes. Based on this, researchers from the University of Alabama conducted a study with a small group of obese men with prediabetes. They compared a form of intermittent fasting called "early time-restricted feeding," where all meals were fit into an early eight-hour period of the day 7 am to 3 pm , or spread out over 12 hours between 7 am and 7 pm.
Both groups maintained their weight did not gain or lose but after five weeks, the eight-hours group had dramatically lower insulin levels and significantly improved insulin sensitivity, as well as significantly lower blood pressure.
The best part? The eight-hours group also had significantly decreased appetite. They weren't starving. Just changing the timing of meals, by eating earlier in the day and extending the overnight fast, significantly benefited metabolism even in people who didn't lose a single pound.
But why does simply changing the timing of our meals to allow for fasting make a difference in our body? An in-depth review of the science of IF recently published in New England Journal of Medicine sheds some light.
Fasting is evolutionarily embedded within our physiology, triggering several essential cellular functions. Flipping the switch from a fed to fasting state does more than help us burn calories and lose weight. The researchers combed through dozens of animal and human studies to explain how simple fasting improves metabolism, lowers blood sugar levels; lessens inflammation, which improves a range of health issues from arthritic pain to asthma; and even helps clear out toxins and damaged cells, which lowers risk for cancer and enhances brain function.
According to metabolic expert Dr. Deborah Wexler, Director of the Massachusetts General Hospital Diabetes Center and associate professor at Harvard Medical School, says "there is evidence to suggest that the circadian rhythm fasting approach, where meals are restricted to an eight to hour period of the daytime, is effective.
So, here's the deal. There is some good scientific evidence suggesting that circadian rhythm fasting, when combined with a healthy diet and lifestyle, can be a particularly effective approach to weight loss, especially for people at risk for diabetes.
However, people with advanced diabetes or who are on medications for diabetes, people with a history of eating disorders like anorexia and bulimia, and pregnant or breastfeeding women should not attempt intermittent fasting unless under the close supervision of a physician who can monitor them.
Adapted from a Harvard Health Blog post by Monique Tello, MD, MPH. Effects of intermittent fasting on health, aging, and disease.
de Cabo R, Mattonson MP. New England Journal of Medicine , December Effect of Alternate-Day Fasting on Weight Loss, Weight Maintenance, and Cardioprotection Among Metabolically Healthy Obese Adults: A Randomized Clinical Trial. JAMA Internal Medicine , May Alternate-day fasting in nonobese subjects: effects on body weight, body composition, and energy metabolism.
American Journal of Clinical Nutrition , January Intermittent fasting interventions for treatment of overweight and obesity in adults: a systematic review and meta-analysis. JBI Database of Systematic Reviews and Implementation Reports, February Metabolic Effects of Intermittent Fasting.
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. Fasting: molecular mechanisms and clinical applications. Cell Metab. Article CAS PubMed PubMed Central Google Scholar. Barnosky AR, Hoddy KK, Unterman TG, Varady KA.
Intermittent fasting vs daily calorie restriction for type 2 diabetes prevention: a review of human findings. Transl Res. Article PubMed Google Scholar. Alkandari JR, Maughan RJ, Roky R, Aziz AR, Karli U. The implications of Ramadan fasting for human health and well-being.
J Sports Sci. Azizi F. Islamic fasting and health. Ann Nutr Metab. Article CAS PubMed Google Scholar. Emami-Naini A, Roomizadeh P, Baradaran A, Abedini A, Abtahi M. Ramadan fasting and patients with renal diseases: a mini review of the literature. J Res Med Sci.
PubMed PubMed Central Google Scholar. Faris MA, Kacimi S, Al-Kurd RA, Fararjeh MA, Bustanji YK, Mohammad MK, Salem ML. Intermittent fasting during Ramadan attenuates proinflammatory cytokines and immune cells in healthy subjects.
Nutr Res. Salim I, Al Suwaidi J, Ghadban W, Alkilani H, Salam AM. Impact of religious Ramadan fasting on cardiovascular disease: a systematic review of the literature.
Curr Med Res Opin. Aziz AR, Chia MY, Low CY, Slater GJ, Png W, Teh KC. Conducting an acute intense interval exercise session during the Ramadan fasting month: what is the optimal time of the day? Chronobiol Int. Bouhlel E, Salhi Z, Bouhlel H, Mdella S, Amamou A, Zaouali M, Mercier J, Bigard X, Tabka Z, Zbidi A, Shephard RJ.
Effect of Ramadan fasting on fuel oxidation during exercise in trained male rugby players. Diabetes Metab. Bouhlel E, Zaouali M, Miled A, Tabka Z, Bigard X, Shephard R. Burke LM, King C. Ramadan fasting and the goals of sports nutrition around exercise.
Chaouachi A, Leiper JB, Chtourou H, Aziz AR, Chamari K. The effects of Ramadan intermittent fasting on athletic performance: recommendations for the maintenance of physical fitness. Javad Fallah S. Ramadan fasting and exercise performance. Asian J Sports Med.
Stannard SR. Ramadan and Its Effect on Fuel Selection during Exercise and Following Exercise Training. Stannard SR, Thompson MW. The effect of participation in Ramadan on substrate selection during submaximal cycling exercise.
J Sci Med Sport. Bhutani S, Klempel MC, Kroeger CM, Trepanowski JF, Varady KA.
Mtabolism fasting Fastong a trendy topic that merabolism repeatedly in my clinic Eating disorder treatment facilities days. I Fasting and metabolism it: restrict 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. Fasring Fasting and metabolism is Healthy appetite suppressant fasting even intermittent fasting makes you cold, sluggish, and prone to weight gain following a refeed. Ad makes sense that depriving your body of nutrients would have a metabolic-shutdown effect. But the meme is only half true. Sure, if you chronically restrict calories—or starve for many days on end—your metabolic rate will tank. Which means the lost weight will come back.
0 thoughts on “Fasting and metabolism”