Intermittent Fasting (IF)

CURATOR

A pinboard by

Tim Squirrell

I study how people in online fitness and nutrition communities construct and negotiate expertise.

PINBOARD SUMMARY

IF has become increasingly popular over recent years as a means of weight loss and regulation.

Lose weight whilst eating whatever you like?

Intermittent fasting is a feeding protocol that involves restricting your food consumption to one window in the day. The idea is that it manipulates your insulin secretion so that you burn more fat than you would if you were eating normally.

How does it work?

Your body is usually in one of two states: fat-storing and fat-burning. This is dictated by the levels of insulin in your bloodstream. Insulin secretion is stimulated by glucose intake; when our body detects glucose, it releases insulin to tell our fat cells to store fatty acids and our other cells to take up glucose. When there's no insulin in our bloodstream, our fat cells release fatty acids. That's when we can burn those fats (instead of glucose) for energy. When we're fasted, there's less insulin in our blood, so there's more fatty acids floating around ready to be burned.

Why does it work?

IF practitioners argue that you can turn yourself into a "fat burning machine by fasting for 16-18 hours a day, and having a "feeding window" of 6-8 hours for men, and 8-12 hours for women.

Is it too good to be true?

The science in IF, as in all areas of nutrition, is disputed. Some studies suggest that it has positive effects on everything from lipid metabolism, to circadian rhythms, to your risk of cardiovascular disease; others suggest the opposite.

So which is it? The answer is probably it depends&amp. If you're only eating eight hours a day, but consuming pure sugar constantly during that time, you're unlikely to get much out of it. But a lot of people find that adhering to one rule makes it easier to adhere to others, and so they clean up their diet when they're doing IF, making them more likely to lose weight that way.

Are they losing weight because of the fasting itself, or is it just a matter of reducing the amount of calories they're consuming because they're restricting their feeding window? It's unclear at the moment, but it's an exciting field with a lot of research questions left to answer!

15 ITEMS PINNED

On the moral responsibility of military robots

Abstract: This article discusses mechanisms and principles for assignment of moral responsibility to intelligent robots, with special focus on military robots. We introduce the concept autonomous power as a new concept, and use it to identify the type of robots that call for moral considerations. It is furthermore argued that autonomous power, and in particular the ability to learn, is decisive for assignment of moral responsibility to robots. As technological development will lead to robots with increasing autonomous power, we should be prepared for a future when people blame robots for their actions. It is important to, already today, investigate the mechanisms that control human behavior in this respect. The results may be used when designing future military robots, to control unwanted tendencies to assign responsibility to the robots. Independent of the responsibility issue, the moral quality of robots’ behavior should be seen as one of many performance measures by which we evaluate robots. How to design ethics based control systems should be carefully investigated already now. From a consequentialist view, it would indeed be highly immoral to develop robots capable of performing acts involving life and death, without including some kind of moral framework.

Pub.: 09 Sep '12, Pinned: 30 Aug '17

Chronic intermittent fasting improves cognitive functions and brain structures in mice.

Abstract: Obesity is a major health issue. Obesity started from teenagers has become a major health concern in recent years. Intermittent fasting increases the life span. However, it is not known whether obesity and intermittent fasting affect brain functions and structures before brain aging. Here, we subjected 7-week old CD-1 wild type male mice to intermittent (alternate-day) fasting or high fat diet (45% caloric supplied by fat) for 11 months. Mice on intermittent fasting had better learning and memory assessed by the Barnes maze and fear conditioning, thicker CA1 pyramidal cell layer, higher expression of drebrin, a dendritic protein, and lower oxidative stress than mice that had free access to regular diet (control mice). Mice fed with high fat diet was obese and with hyperlipidemia. They also had poorer exercise tolerance. However, these obese mice did not present significant learning and memory impairment or changes in brain structures or oxidative stress compared with control mice. These results suggest that intermittent fasting improves brain functions and structures and that high fat diet feeding started early in life does not cause significant changes in brain functions and structures in obese middle-aged animals.

Pub.: 12 Jun '13, Pinned: 14 Jul '17

Intermittent Fasting Pretreatment Prevents Cognitive Impairment in a Rat Model of Chronic Cerebral Hypoperfusion.

Abstract: Background: Whether intermittent fasting (IF) pretreatment can prevent vascular cognitive dysfunction remains unknown to our knowledge.Objective: We investigated the effects and underlying mechanisms of IF pretreatment on cognitive dysfunction in a permanent 2-vessel occlusion (2VO) vascular dementia rat model.Methods: Male Wistar rats weighing 200 g were subjected to either IF or ad libitum feeding for 12 wk before 2VO surgery. Rats in the IF protocol underwent alternative-day feed deprivation (FD). Memory of the animals was assessed by using the Morris water maze (MWM) and the novel object recognition (NOR) test 6 wk after the surgery. After behavioral testing, malondialdehyde and glutathione concentrations, superoxide dismutase (SOD) activity, gene expression of antioxidative enzymes, inflammatory protein concentrations, and microglia density were determined in the hippocampus of rats.Results: 2-vessel occlusion operation ad libitum (2VO-AL) rats had significantly longer escape latencies on day 4 of the training phase and spent a lower percentage of time in the target quadrant (25% compared with 38% and 41%) in the MWM, and had lower discrimination ratios (47% compared with 65% and 67%) in the NOR test than 2-vessel operation and alternate-day feed deprivation (2VO-FD) and sham operation ad libitum (Sham-AL) rats, respectively (P < 0.05). This indicates that IF helps to prevent vascular cognitive deficits. 2VO-AL rats also had higher malondialdehyde (3.54 compared with 2.15 and 1.66 nmol/mg protein) and lower glutathione concentrations (53.25 compared with 66.41 and 91.71 nmol/mg protein), lower SOD activity (100.1 compared with 133.3 and 138.5 U/mg protein), lower gene expression of antioxidative enzymes, higher expression of inflammatory proteins, and higher microglia density in the hippocampus than 2VO-FD and Sham-AL rats, respectively (P < 0.05). This suggests that IF has antioxidative and anti-inflammatory effects.Conclusions: IF pretreatment provided sustained neuroprotection in a rat model of vascular dementia. These effects were associated with reduced oxidative stress and neuroinflammation.

Pub.: 19 May '17, Pinned: 14 Jul '17

Effects of intermittent fasting on body composition and clinical health markers in humans.

Abstract: Intermittent fasting is a broad term that encompasses a variety of programs that manipulate the timing of eating occasions by utilizing short-term fasts in order to improve body composition and overall health. This review examines studies conducted on intermittent fasting programs to determine if they are effective at improving body composition and clinical health markers associated with disease. Intermittent fasting protocols can be grouped into alternate-day fasting, whole-day fasting, and time-restricted feeding. Alternate-day fasting trials of 3 to 12 weeks in duration appear to be effective at reducing body weight (≈3%-7%), body fat (≈3-5.5 kg), total cholesterol (≈10%-21%), and triglycerides (≈14%-42%) in normal-weight, overweight, and obese humans. Whole-day fasting trials lasting 12 to 24 weeks also reduce body weight (≈3%-9%) and body fat, and favorably improve blood lipids (≈5%-20% reduction in total cholesterol and ≈17%-50% reduction in triglycerides). Research on time-restricted feeding is limited, and clear conclusions cannot be made at present. Future studies should examine long-term effects of intermittent fasting and the potential synergistic effects of combining intermittent fasting with exercise.

Pub.: 17 Sep '15, Pinned: 12 Apr '17

Impact of intermittent fasting on glucose homeostasis.

Abstract: This article provides an overview of the most recent human trials that have examined the impact of intermittent fasting on glucose homeostasis.Our literature search retrieved one human trial of alternate day fasting, and three trials of Ramadan fasting published in the past 12 months. Current evidence suggests that 8 weeks of alternate day fasting that produces mild weight loss (4% from baseline) has no effect on glucose homeostasis. As for Ramadan fasting, decreases in fasting glucose, insulin, and insulin resistance have been noted after 4 weeks in healthy normal weight individuals with mild weight loss (1-2% from baseline). However, Ramadan fasting may have little impact on glucoregulatory parameters in women with polycystic ovarian syndrome who failed to observe weight loss.Whether intermittent fasting is an effective means of regulating glucose homeostasis remains unclear because of the scarcity of studies in this area. Large-scale, longer-term randomized controlled trials will be required before the use of fasting can be recommended for the prevention and treatment of metabolic diseases.

Pub.: 04 May '16, Pinned: 12 Apr '17

Comparison of High-Protein, Intermittent Fasting Low-Calorie Diet and Heart Healthy Diet for Vascular Health of the Obese.

Abstract: It has been debated whether different diets are more or less effective in long-term weight loss success and cardiovascular disease prevention among men and women. To further explore these questions, the present study evaluated the combined effects of a high-protein, intermittent fasting, low-calorie diet plan compared with a heart healthy diet plan during weight loss, and weight loss maintenance on blood lipids and vascular compliance of obese individuals.The experiment involved 40 obese adults (men, n = 21; women, n = 19) and was divided into two phases: (a) 12-week high-protein, intermittent fasting, low-calorie weight loss diet comparing men and women (Phase 1) and (b) a 1-year weight maintenance phase comparing high-protein, intermittent fasting with a heart healthy diet (Phase 2). Body weight, body mass index (BMI), blood lipids, and arterial compliance outcomes were assessed at weeks 1 (baseline control), 12 (weight loss), and 64 (12 + 52 week; weight loss maintenance).At the end of weight loss intervention, concomitant reductions in body weight, BMI and blood lipids were observed, as well as enhanced arterial compliance. No sex-specific differences in responses were observed. During phase 2, the high-protein, intermittent fasting group demonstrated a trend for less regain in BMI, low-density lipoprotein (LDL), and aortic pulse wave velocity than the heart healthy group.Our results suggest that a high-protein, intermittent fasting and low-calorie diet is associated with similar reductions in BMI and blood lipids in obese men and women. This diet also demonstrated an advantage in minimizing weight regain as well as enhancing arterial compliance as compared to a heart healthy diet after 1 year.

Pub.: 14 Sep '16, Pinned: 12 Apr '17

Behavioral Sciences, Vol. 7, Pages 4: Potential Benefits and Harms of Intermittent Energy Restriction and Intermittent Fasting Amongst Obese, Overweight and Normal Weight Subjects—A Narrative Review of Human and Animal Evidence

Abstract: Intermittent energy restriction (IER) has become popular as a means of weight control amongst people who are overweight and obese, and is also undertaken by normal weight people hoping spells of marked energy restriction will optimise their health. This review summarises randomised comparisons of intermittent and isoenergetic continuous energy restriction for weight loss to manage overweight and obesity. It also summarises the potential beneficial or adverse effects of IER on body composition, adipose stores and metabolic effects from human studies, including studies amongst normal weight subjects and relevant animal experimentation. Six small short term (<6 month) studies amongst overweight or obese individuals indicate that intermittent energy restriction is equal to continuous restriction for weight loss, with one study reporting greater reductions in body fat, and two studies reporting greater reductions in HOMA insulin resistance in response to IER, with no obvious evidence of harm. Studies amongst normal weight subjects and different animal models highlight the potential beneficial and adverse effects of intermittent compared to continuous energy restriction on ectopic and visceral fat stores, adipocyte size, insulin resistance, and metabolic flexibility. The longer term benefits or harms of IER amongst people who are overweight or obese, and particularly amongst normal weight subjects, is not known and is a priority for further investigation.

Pub.: 19 Jan '17, Pinned: 12 Apr '17

The Effects of Intermittent Fasting and a High-Protein Diet on Biochemical and Anthropometric Measurements in Type 2 Diabetes Mellitus

Abstract: Background: Intermittent fasting (IF) has been shown to have beneficial effects on certain metabolic parameters in animals and healthy subjects.

Pub.: 01 Oct '16, Pinned: 12 Apr '17

Patient Perceptions of Intermittent Fasting in Individuals with Type 2 Diabetes Mellitus: A Pilot Study

Abstract: Background: Intermittent fasting (IF) is increasingly being used as a dietary method by people trying to lose weight.

Pub.: 01 Oct '16, Pinned: 12 Apr '17

Effects of eight weeks of time-restricted feeding (16/8) on basal metabolism, maximal strength, body composition, inflammation, and cardiovascular risk factors in resistance-trained males.

Abstract: Intermittent fasting (IF) is an increasingly popular dietary approach used for weight loss and overall health. While there is an increasing body of evidence demonstrating beneficial effects of IF on blood lipids and other health outcomes in the overweight and obese, limited data are available about the effect of IF in athletes. Thus, the present study sought to investigate the effects of a modified IF protocol (i.e. time-restricted feeding) during resistance training in healthy resistance-trained males.Thirty-four resistance-trained males were randomly assigned to time-restricted feeding (TRF) or normal diet group (ND). TRF subjects consumed 100 % of their energy needs in an 8-h period of time each day, with their caloric intake divided into three meals consumed at 1 p.m., 4 p.m., and 8 p.m. The remaining 16 h per 24-h period made up the fasting period. Subjects in the ND group consumed 100 % of their energy needs divided into three meals consumed at 8 a.m., 1 p.m., and 8 p.m. Groups were matched for kilocalories consumed and macronutrient distribution (TRF 2826 ± 412.3 kcal/day, carbohydrates 53.2 ± 1.4 %, fat 24.7 ± 3.1 %, protein 22.1 ± 2.6 %, ND 3007 ± 444.7 kcal/day, carbohydrates 54.7 ± 2.2 %, fat 23.9 ± 3.5 %, protein 21.4 ± 1.8). Subjects were tested before and after 8 weeks of the assigned diet and standardized resistance training program. Fat mass and fat-free mass were assessed by dual-energy x-ray absorptiometry and muscle area of the thigh and arm were measured using an anthropometric system. Total and free testosterone, insulin-like growth factor 1, blood glucose, insulin, adiponectin, leptin, triiodothyronine, thyroid stimulating hormone, interleukin-6, interleukin-1β, tumor necrosis factor α, total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and triglycerides were measured. Bench press and leg press maximal strength, resting energy expenditure, and respiratory ratio were also tested.After 8 weeks, the 2 Way ANOVA (Time * Diet interaction) showed a decrease in fat mass in TRF compared to ND (p = 0.0448), while fat-free mass, muscle area of the arm and thigh, and maximal strength were maintained in both groups. Testosterone and insulin-like growth factor 1 decreased significantly in TRF, with no changes in ND (p = 0.0476; p = 0.0397). Adiponectin increased (p = 0.0000) in TRF while total leptin decreased (p = 0.0001), although not when adjusted for fat mass. Triiodothyronine decreased in TRF, but no significant changes were detected in thyroid-stimulating hormone, total cholesterol, high-density lipoprotein, low-density lipoprotein, or triglycerides. 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.

Pub.: 16 Oct '16, Pinned: 12 Apr '17

Impact of Intermittent Fasting on Health and Disease Processes

Abstract: Humans in modern societies typically consume food at least three times daily, while laboratory animals are fed ad libitum. Overconsumption of food with such eating patterns often leads to metabolic morbidities (insulin resistance, excessive accumulation of visceral fat, etc.), particularly when associated with a sedentary lifestyle. Because animals, including humans, evolved in environments where food was relatively scarce, they developed numerous adaptations that enabled them to function at a high level, both physically and cognitively, when in a food-deprived/fasted state. Intermittent fasting (IF) encompasses eating patterns in which individuals go extended time periods (e.g., 16–48 hours) with little or no energy intake, with intervening periods of normal food intake, on a recurring basis. We use the term periodic fasting (PF) to refer to IF with periods of fasting or fasting mimicking diets lasting from 2 to as many as 21 or more days. In laboratory rats and mice IF and PF have profound beneficial effects on many different indices of health and, importantly, can counteract disease processes and improve functional outcome in experimental models of a wide range of age-related disorders including diabetes, cardiovascular disease, cancers and neurological disorders such as Alzheimer’s disease Parkinson’s disease and stroke. Studies of IF (e.g., 60% energy restriction on 2 days per week or every other day), PF (e.g., a 5 day diet providing 750–1100 kcal) and time-restricted feeding (TRF; limiting the daily period of food intake to 8 hours or less) in normal and overweight human subjects have demonstrated efficacy for weight loss and improvements in multiple health indicators including insulin resistance and reductions in risk factors for cardiovascular disease. The cellular and molecular mechanisms by which IF improves health and counteracts disease processes involve activation of adaptive cellular stress response signaling pathways that enhance mitochondrial health, DNA repair and autophagy. PF also promotes stem cell-based regeneration as well as long-lasting metabolic effects. Randomized controlled clinical trials of IF versus PF and isoenergetic continuous energy restriction in human subjects will be required to establish the efficacy of IF in improving general health, and preventing and managing major diseases of aging.

Pub.: 31 Oct '16, Pinned: 12 Apr '17

Effects of intermittent fasting on glucose and lipid metabolism.

Abstract: Two intermittent fasting variants, intermittent energy restriction (IER) and time-restricted feeding (TRF), have received considerable interest as strategies for weight-management and/or improving metabolic health. With these strategies, the pattern of energy restriction and/or timing of food intake are altered so that individuals undergo frequently repeated periods of fasting. This review provides a commentary on the rodent and human literature, specifically focusing on the effects of IER and TRF on glucose and lipid metabolism. For IER, there is a growing evidence demonstrating its benefits on glucose and lipid homeostasis in the short-to-medium term; however, more long-term safety studies are required. Whilst the metabolic benefits of TRF appear quite profound in rodents, findings from the few human studies have been mixed. There is some suggestion that the metabolic changes elicited by these approaches can occur in the absence of energy restriction, and in the context of IER, may be distinct from those observed following similar weight-loss achieved via modest continuous energy restriction. Mechanistically, the frequently repeated prolonged fasting intervals may favour preferential reduction of ectopic fat, beneficially modulate aspects of adipose tissue physiology/morphology, and may also impinge on circadian clock regulation. However, mechanistic evidence is largely limited to findings from rodent studies, thus necessitating focused human studies, which also incorporate more dynamic assessments of glucose and lipid metabolism. Ultimately, much remains to be learned about intermittent fasting (in its various forms); however, the findings to date serve to highlight promising avenues for future research.

Pub.: 17 Jan '17, Pinned: 12 Apr '17

Ramadan fasting in Saudi Arabia is associated with altered expression of CLOCK, DUSP and IL-1alpha genes, as well as changes in cardiometabolic risk factors.

Abstract: During the fasting month of Ramadan, practicing Saudis develop severe disturbances in sleeping and feeding patterns. Concomitantly, cortisol circadian rhythm is abolished, diurnal cortisol levels are elevated and circulating levels of several adipokines are altered favouring insulin resistance.To examine changes in the expression of CLOCK and glucocorticoid-controlled genes, such as DUSP1 and IL-1α in Saudi adults before and during Ramadan, and to investigate possible associations with selected cardiometabolic risk factors.Healthy young volunteers (5 females, 18 males; mean age +SEM = 23.2 +1.2 years) were evaluated before Ramadan and two weeks into it. Blood samples were collected at 9 am (±1 hour) and twelve hours later for determination of serum lipid profile, high sensitivity CRP (hsCRP), and adiponectin. The expression of CLOCK, DUSP1 and IL-1α was evaluated in circulating leukocytes.Mean levels of GGT and morning adiponectin decreased, while those of LDL-c/ HDL-c and atherogenic index (AI) increased significantly in Ramadan compared to Shabaan. There was no significant difference between morning and evening adiponectin during Ramadan, while the diurnal rhythm of hsCRP was lost. CLOCK gene expression mean was significantly higher in morning than in evening during Shabaan. Mean morning and evening DUSP1 mRNA levels showed significant increase during Ramadan compared to Shabaan, however, its diurnal rhythm was maintained. Morning IL-1α mRNA expression remained significantly higher than in the evening during Ramadan, but was markedly decreased compared to Shabaan.Ramadan fasting in Saudi Arabia is associated with improvements in some cardiometabolic risk factors, such as circulating GGT and hsCRP and leukocyte expression of IL-1α mRNA, suggesting that intermittent fasting might have a beneficial component. These benefits may be offset by the previously reported dysregulation in the circadian rhythm, excess glucocorticoid levels and action, and insulin resistance, explaining increased prevalence of cardiometabolic disorders and type 2 diabetes mellitus.

Pub.: 07 Apr '17, Pinned: 12 Apr '17

Meal Timing and Frequency: Implications for Cardiovascular Disease Prevention: A Scientific Statement From the American Heart Association.

Abstract: Eating patterns are increasingly varied. Typical breakfast, lunch, and dinner meals are difficult to distinguish because skipping meals and snacking have become more prevalent. Such eating styles can have various effects on cardiometabolic health markers, namely obesity, lipid profile, insulin resistance, and blood pressure. In this statement, we review the cardiometabolic health effects of specific eating patterns: skipping breakfast, intermittent fasting, meal frequency (number of daily eating occasions), and timing of eating occasions. Furthermore, we propose definitions for meals, snacks, and eating occasions for use in research. Finally, data suggest that irregular eating patterns appear less favorable for achieving a healthy cardiometabolic profile. Intentional eating with mindful attention to the timing and frequency of eating occasions could lead to healthier lifestyle and cardiometabolic risk factor management.

Pub.: 01 Feb '17, Pinned: 12 Apr '17

"Is there an optimal diet for weight management and metabolic health?"

Abstract: Individuals can lose body weight and improve health status on a wide range of energy (calorie) restricted dietary interventions. In this paper, we have reviewed the effectiveness of the most commonly utilized diets, including low-fat, low-carbohydrate and Mediterranean approaches in addition to commercial slimming programmes, meal replacements and newly-popularized intermittent fasting diets. We also consider the role of artificial sweeteners in weight management. Low-fat diets tend to improve LDL-cholesterol most, whilst lower-carbohydrate diets may preferentially improve triglycerides and HDL-cholesterol, however differences between diets are marginal. Weight loss improves almost all obesity related co-morbidities and metabolic markers, regardless of the macronutrient composition of the diet, but individuals do vary in preferences and ability to adhere to different diets. Optimizing adherence is the most important factor for weight loss success, and this is enhanced by regular professional contact and supportive behavioral change programs. Maintaining weight losses in the long-term remains the biggest challenge, and is undermined by an 'obesogenic' environment and biological adaptations that accompany weight loss.

Pub.: 20 Feb '17, Pinned: 12 Apr '17