Efficacy and safety of prolonged water fasting: a narrative review of human trials

The goal of this narrative review is to summarize the effects of prolonged fasting on various metabolic health measures, including body weight, blood pressure, plasma lipids, and glycemic control. Prolonged fasting is characterized by consciously eating little to no food or caloric beverages for several days to weeks. Results reveal that prolonged fasting for 5-20 days produces potent increases in circulating ketones, and mild to moderate weight loss of 2-10%. Approximately two-thirds of the weight lost is lean mass, and one-third is fat mass. The excessive lean mass loss suggests that prolonged fasting may increase the breakdown of muscle proteins, which is a concern. Systolic and diastolic blood pressure consistently decreased with prolonged fasting. However, the impact of these protocols on plasma lipids is less clear. While some trials demonstrate decreases in LDL cholesterol and triglycerides, others show no benefit. With regard to glycemic control, reductions in fasting glucose, fasting insulin, insulin resistance, and glycated hemoglobin (HbA1c) were noted in adults with normoglycemia. In contrast, these glucoregulatory factors remained unchanged in patients with type 1 or type 2 diabetes. The effects of refeeding were also examined in a few trials. It was shown that 3-4 months after the fast was completed, all metabolic benefits were no longer observed, even when weight loss was maintained. With regard to adverse events, metabolic acidosis, headaches, insomnia, and hunger were observed in some studies. In summary, prolonged fasting appears to be a moderately safe diet therapy that can produce clinically significant weight loss (>5%) over a few days or weeks. However, the ability of these protocols to produce sustained improvements in metabolic markers warrants further investigation.

Design of a Remote Time-Restricted Eating and Mindfulness Intervention to Reduce Risk Factors Associated with Early-Onset Colorectal Cancer Development among Young Adults

Early-onset colorectal cancer (EOCRC) is defined as a diagnosis of colorectal cancer (CRC) in individuals younger than 50 years of age. While overall CRC rates in the United States (US) decreased between 2001 and 2018, EOCRC rates have increased. This research project aims to evaluate the feasibility and acceptability of Time-Restricted Eating (TRE), Mindfulness, or TRE combined with Mindfulness among young to middle-aged adults at risk of EOCRC. Forty-eight participants will be randomly assigned to one of four groups: TRE, Mindfulness, TRE and Mindfulness, or Control. Data on feasibility, adherence, and acceptability will be collected. Measures assessed at baseline and post-intervention will include body weight, body composition, dietary intake, physical activity, sleep behavior, circulating biomarkers, hair cortisol, and the gut microbiome. The effects of the intervention on the following will be examined: (1) acceptability and feasibility; (2) body weight, body composition, and adherence to TRE; (3) circulating metabolic, inflammation, and oxidative stress biomarkers; (4) intestinal inflammation; and (5) the gut microbiome. TRE, combined with Mindfulness, holds promise for stress reduction and weight management among individuals at risk of EOCRC. The results of this pilot study will inform the design and development of larger trials aimed at preventing risk factors associated with EOCRC.

Time-restricted eating: Watching the clock to treat obesity

Time-restricted eating (TRE) has become a popular strategy to treat obesity. TRE involves confining the eating window to 4-10 h per day and fasting for the remaining hours (14-20 h fast). During the eating window, individuals are not required to monitor food intake. The sudden rise in popularity of TRE is most likely due to its simplicity and the fact that it does not require individuals to count calories to lose weight. This feature of TRE may appeal to certain individuals with obesity, and this could help produce lasting metabolic health improvements. The purpose of this review is to summarize current evidence from randomized clinical trials of TRE (without calorie counting) on body weight and metabolic risk factors. The efficacy of TRE in various populations groups, including those with obesity, type 2 diabetes (T2DM), and polycystic ovary syndrome (PCOS), is also examined.

Effect of Time-Restricted Eating on Weight Loss in Adults With Type 2 Diabetes: A Randomized Clinical Trial

Importance

Time-restricted eating (TRE) has become increasingly popular, yet longer-term randomized clinical trials have not evaluated its efficacy and safety in patients with type 2 diabetes (T2D).

Objective

To determine whether TRE is more effective for weight reduction and glycemic control than daily calorie restriction (CR) or a control condition in adults with T2D.

Design, Setting, and Participants

This 6-month, parallel-group, randomized clinical trial was performed between January 25, 2022, and April 1, 2023, at the University of Illinois Chicago. Participants were aged 18 to 80 years with obesity and T2D. Data analysis was based on intention to treat.

Interventions

Participants were randomized to 1 of 3 groups: 8-hour TRE (eating 12 to 8 pm only, without calorie counting), CR (25% energy restriction daily), or control.

Main Outcomes and Measures

The primary outcome measure was change in body weight by month 6. Secondary outcomes included changes in hemoglobin A1c (HbA1c) levels and metabolic risk factors.

Results

Seventy-five participants were enrolled with a mean (SD) age of 55 (12) years. The mean (SD) body mass index (calculated as weight in kilograms divided by height in meters squared) was 39 (7) and the mean (SD) HbA1c level was 8.1% (1.6%). A total of 53 participants (71%) were women. One participant (1%) was Asian, 30 (40%) were Hispanic White, 40 (53%) were non-Hispanic Black, and 4 (5%) were non-Hispanic White. Participants in the TRE group were adherent with their eating window on a mean (SD) of 6.1 (0.8) days per week, and 17 (68%) in the CR group were adherent with their prescribed calorie goals over 6 months. The mean (SD) reduction in energy intake was -313 (509) kcal/d for TRE, -197 (426) kcal/d for CR, and -16 (439) kcal/d for controls. By month 6, body weight decreased significantly in the TRE group (-3.56% [95% CI, -5.92% to -1.20%]; P = .004) but not the CR group (-1.78% [95% CI, -3.67% to 0.11%]; P = .06), relative to controls. Levels of HbA1c decreased in the TRE (-0.91% [95% CI, -1.61% to -0.20%]) and CR (-0.94% [95% CI, -1.59% to -0.30%]) groups, relative to controls, with no differences between the TRE and CR groups. Time in euglycemic range, medication effect score, blood pressure, and plasma lipid levels did not differ among groups. No serious adverse events were reported.

Conclusions and relevance

This randomized clinical trial found that a TRE diet strategy without calorie counting was effective for weight loss and lowering of HbA1c levels compared with daily calorie counting in a sample of adults with T2D. These findings will need to be confirmed by larger RCTs with longer follow-up.

Trial Registration

ClinicalTrials.gov Identifier: NCT05225337.

Time-Restricted Eating Without Calorie Counting for Weight Loss in a Racially Diverse Population : A Randomized Controlled Trial

BACKGROUND

Time-restricted eating (TRE), without calorie counting, has become a popular weight loss strategy, yet long-term randomized trials evaluating its efficacy are limited.

OBJECTIVE

To determine whether TRE is more effective for weight control and cardiometabolic risk reduction compared with calorie restriction (CR) or control.

DESIGN

12-month randomized controlled trial. (ClinicalTrials.gov: NCT04692532).

SETTING

University of Illinois Chicago from January 2021 to September 2022.

PARTICIPANTS

90 adults with obesity.

INTERVENTION

8-hour TRE (eating between noon and 8:00 p.m. only, without calorie counting), CR (25% energy restriction daily), or control (eating over a period of 10 or more hours per day). Participants were not blinded.

MEASUREMENTS

Change in body weight, metabolic markers, and energy intake by month 12.

RESULTS

Seventy-seven persons completed the study. Mean age was 40 years (SD, 11), 33% were Black, and 46% were Hispanic. Mean reduction in energy intake was -425 kcal/d (SD, 531) for TRE and -405 kcal/d (SD, 712) for CR. Compared with the control group, weight loss by month 12 was -4.61 kg (95% CI, -7.37 to -1.85 kg; P ≤ 0.01) (-4.87% [CI, -7.61% to -2.13%]) for the TRE group and -5.42 kg (CI, -9.13 to -1.71 kg; P ≤ 0.01) (-5.30% [CI, -9.06% to -1.54%]) for the CR group, with no statistically significant difference between TRE and CR (0.81 kg [CI, -3.07 to 4.69 kg; P = 0.68]) (0.43% [CI, -3.48% to 4.34%]).

LIMITATION

Not blinded, not powered to detect relatively large differences in weight loss, and lack of adjustment for multiple comparisons.

CONCLUSION

Time-restricted eating is more effective in producing weight loss when compared with control but not more effective than CR in a racially diverse population.

PRIMARY FUNDING SOURCE

National Institutes of Health, National Institute of Diabetes and Digestive and Kidney Diseases.

Protocol for measuring intrahepatic triglyceride content in adults with non-alcohol fatty liver disease

Here, we present a protocol for conducting magnetic resonance imaging proton density fat fraction (MRI-PDFF) to measure intrahepatic triglyceride (IHTG) content in adults with non-alcohol fatty liver disease (NAFLD). We describe steps for screening patients for NAFLD, MRI-PDFF scanning, and using MRI-PDFF data to quantify IHTG. This protocol can be repeated sequentially and used in weight loss trials. However, it is limited to patients with NAFLD as it does not assess non-alcoholic steatohepatitis or hepatic fibrosis. For complete details on the use and execution of this protocol, please refer to Ezpeleta et al. (2023).¹.

Effect of time-restricted eating on sex hormone levels in premenopausal and postmenopausal females

OBJECTIVE

Concerns have been raised regarding the impact of time-restricted eating (TRE) on sex hormones in females. This study examined how TRE affects sex steroids in premenopausal and postmenopausal females.

METHODS

This is a secondary analysis of an 8-week TRE study (4- to 6-hour eating window) conducted in adults with obesity. Men and perimenopausal females were excluded. Females were classified into two groups based on menstrual status: premenopausal (n = 12) or postmenopausal (n = 11).

RESULTS

After 8 weeks, body weight decreased in premenopausal females (-3% ± 2%) and postmenopausal females (-4% ± 2%) (main effect of time, p < 0.001), with no difference between groups (no group × time interaction). Circulating levels of testosterone, androstenedione, and sex hormone binding globulin (SHBG) did not change in either group (no group × time interaction). Dehydroepiandrosterone (DHEA) concentrations decreased (p < 0.05) in premenopausal (-14% ± 32%) and postmenopausal females (-13% ± 34%; main effect of time, p = 0.03), with no difference between groups. Estradiol, estrone, and progesterone were measured only in postmenopausal females, and they remained unchanged.

CONCLUSIONS

In premenopausal females, androgens and SHBG remained unchanged during TRE, whereas DHEA decreased. In postmenopausal females, estrogens, progesterone, androgens, and SHBG did not change, but DHEA was reduced.

Effect of alternate day fasting combined with aerobic exercise on non-alcoholic fatty liver disease: A randomized controlled trial

Innovative non-pharmacological lifestyle strategies to treat non-alcoholic fatty liver disease (NAFLD) are critically needed. This study compared the effects of alternate day fasting (ADF) combined with exercise to fasting alone, or exercise alone, on intrahepatic triglyceride (IHTG) content. Adults with obesity and NAFLD (n = 80, 81% female, age: 23-65 years) were randomized to 1 of 4 groups for 3 months: combination of ADF (600 kcal/2,500 kJ "fast day" alternated with an ad libitum intake "feast day") and moderate-intensity aerobic exercise (5 session per week, 60 min/session); ADF alone; exercise alone; or a no-intervention control group. By month 3, IHTG content was significantly reduced in the combination group (-5.48%; 95% CI, -7.77% to -3.18%), compared with the exercise group (-1.30%; 95% CI, -3.80% to 1.20%; p = 0.02) and the control group (-0.17%; 95% CI, -2.17% to 1.83%; p < 0.01) but was not significantly different versus the ADF group (-2.25%; 95% CI, -4.46% to -0.04%; p = 0.05). Body weight, fat mass, waist circumference, and alanine transaminase (ALT) levels significantly decreased, while insulin sensitivity significantly increased in the combination group compared with the control group. Lean mass, aspartate transaminase (AST), HbA1c, blood pressure, plasma lipids, liver fibrosis score, and hepatokines (fetuin-A, FGF-21, and selenoprotein P) did not differ between groups. Combining intermittent fasting with exercise is effective for reducing hepatic steatosis in patients with NAFLD but may offer no additional benefit versus fasting alone.

The basis and design for time-restricted eating compared with daily calorie restriction for weight loss and colorectal cancer risk reduction trial (TRE-CRC trial)

OBJECTIVE

Approximately 42% of American adults are living with obesity, increasing their risk of colorectal cancer (CRC). Efficacious approaches to prevent and treat obesity may reduce CRC incidence. Daily calorie restriction (Cal-R) is the most common approach to treating obesity, yet clinically meaningful weight loss is elusive owing to waning adherence. Time-restricted eating (TRE) consists of consuming foods within a specified time frame, creating a natural calorie deficit. TRE in animals shows cancer protective effects. In humans, TRE is safe and acceptable among adults with obesity, producing ~3% to 5% weight loss and reductions in oxidative stress and insulin resistance. However, TRE has not been tested rigorously for CRC preventive effects.

METHODS

The authors describe a 12-month randomized controlled trial of 8-hour TRE (ad libitum 12 PM-8 PM), Cal-R (25% restriction daily), or Control among 255 adults at increased risk for CRC and with obesity.

RESULTS

Effects on the following will be examined: 1) body weight, body composition, and adherence; 2) circulating metabolic, inflammation, and oxidative stress biomarkers; 3) colonic mucosal gene expression profiles and tissue microenvironment; and 4) maintenance of benefits on body weight/composition and CRC risk markers.

CONCLUSIONS

This study will examine efficacious lifestyle strategies to treat obesity and reduce CRC risk among individuals with obesity.

Effect of Intermittent Fasting on Reproductive Hormone Levels in Females and Males: A Review of Human Trials

Intermittent fasting is a popular diet for weight loss, but concerns have been raised regarding the effects of fasting on the reproductive health of women and men. Accordingly, we conducted this literature review to clarify the effects of fasting on reproductive hormone levels in humans. Our results suggest that intermittent fasting decreases androgen markers (i.e., testosterone and the free androgen index (FAI)) while increasing sex hormone-binding globulin (SHBG) levels in premenopausal females with obesity. This effect was more likely to occur when food consumption was confined to earlier in the day (eating all food before 4 pm). In contrast, fasting did not have any effect on estrogen, gonadotropins, or prolactin levels in women. As for men, intermittent fasting reduced testosterone levels in lean, physically active, young males, but it did not affect SHBG concentrations. Interestingly, muscle mass and muscular strength were not negatively affected by these reductions in testosterone. In interpreting these findings, it is important to note that very few studies have been conducted on this topic. Thus, it is difficult to draw solid conclusions at present. From the limited data presented here, it is possible that intermittent fasting may decrease androgen markers in both genders. If this is the case, these results would have varied health implications. On the one hand, fasting may prove to be a valuable tool for treating hyperandrogenism in females with polycystic ovarian syndrome (PCOS) by improving menstruation and fertility. On the other hand, fasting may be shown to decrease androgens among males, which could negatively affect metabolic health and libido. More research is warranted to confirm these preliminary findings.

Clinical application of intermittent fasting for weight loss: progress and future directions

Intermittent fasting diets have become very popular in the past few years, as they can produce clinically significant weight loss. These diets can be defined, in the simplest of terms, as periods of fasting alternating with periods of eating. The most studied forms of intermittent fasting include: alternate day fasting (0-500 kcal per 'fast day' alternating with ad libitum intake on 'feast days'); the 5:2 diet (two fast days and five feast days per week) and time-restricted eating (only eating within a prescribed window of time each day). Despite the recent surge in the popularity of fasting, only a few studies have examined the health benefits of these diets in humans. The goal of this Review is to summarize these preliminary findings and give insights into the effects of intermittent fasting on body weight and risk factors for cardiometabolic diseases in humans. This Review also assesses the safety of these regimens, and offers some practical advice for how to incorporate intermittent fasting diets into everyday life. Recommendations for future research are also presented.

The effect of 4-h versus 6-h time restricted feeding on sleep quality, duration, insomnia severity and obstructive sleep apnea in adults with obesity

BACKGROUND

Time restricted feeding (TRF) involves deliberately restricting the times during which energy is ingested. Preliminary findings suggest that 8-10-h TRF improves sleep. However, the effects of shorter TRF windows (4-6 h) on sleep, remain unknown.

AIMS

This study compared the effects of 4-h versus 6-h TRF on sleep quality, duration, insomnia severity and the risk of obstructive sleep apnea.

METHODS

Adults with obesity (n = 49) were randomized into one of three groups: 4-h TRF (eating only between 3 and 7 p.m.), 6-h TRF (eating only between 1 and 7 p.m.), or a control group (no meal timing restrictions) for 8 weeks.

RESULTS

After 8 weeks, body weight decreased (p < 0.001) similarly by 4-h TRF (-3.9 ± 0.4 kg) and 6-h TRF (-3.4 ± 0.4 kg), versus controls. Sleep quality, measured by the Pittsburgh Sleep Quality Index (PSQI), did not change by 4-h TRF (baseline: 5.9 ± 0.7; week 8: 4.8 ± 0.6) or 6-h TRF (baseline: 6.4 ± 0.8; week 8: 5.3 ± 0.9), versus controls. Wake time, bedtime, sleep duration and sleep onset latency also remained unchanged. Insomnia severity did not change by 4-h TRF (baseline: 4.4 ± 1.0; week 8: 4.7 ± 0.9) or 6-h TRF (baseline: 8.3 ± 1.2; week 8: 5.5 ± 1.1), versus controls. Percent of participants reporting obstructive sleep apnea symptoms did not change by 4-h TRF (baseline: 44%; week 8: 25%) or 6-h TRF (baseline: 47%; week 8: 20%), versus controls.

CONCLUSION

These findings suggest that 4- and 6-h TRF have no effect on sleep quality, duration, insomnia severity, or the risk of obstructive sleep apnea.

Current Evidence and Directions for Intermittent Fasting During Cancer Chemotherapy

Almost 40% of the adult population in the USA will be diagnosed with cancer in their lifetime. Diet is a modifiable factor which is known to affect cancer risk and recurrence. Yet, little is known about how diet influences cancer treatment outcomes. Intermittent fasting, characterized by periods of abstaining from foods and beverages alternated with periods of ad libitum intake, when adopted in the context of chemotherapy, has shown promise in preclinical models resulting in decreased vomiting, diarrhea, visible discomfort, and improved insulin sensitivity and efficacy of chemotherapeutic treatment. Although intermittent fasting during receipt of chemotherapy has been well-established in preclinical models, limited numbers of human studies are now being reported. This review aims to survey the current data examining the effect of intermittent fasting on chemotherapy efficacy, patient treatment outcomes, patient centered outcomes, and circulating biomarkers associated with cancer. Available data show that periodic fasting, a form of intermittent fasting, may hold potential to improve the effectiveness of chemotherapy, decrease treatment-related side effects and cancer-promoting factors such as insulin, while ameliorating treatment-related decreases in quality of life and daily functioning. Larger controlled periodic fasting trials, including exploration of alternate forms of intermittent fasting, are needed to better elucidate the effect of intermittent fasting on treatment and patient outcomes during chemotherapy.

Cardiometabolic Benefits of Intermittent Fasting

This review aims to summarize the effects of intermittent fasting on markers of cardiometabolic health in humans. All forms of fasting reviewed here-alternate-day fasting (ADF), the 5:2 diet, and time-restricted eating (TRE)-produced mild to moderate weight loss (1-8% from baseline) and consistent reductions in energy intake (10-30% from baseline). These regimens may benefit cardiometabolic health by decreasing blood pressure, insulin resistance, and oxidative stress. Low-density lipoprotein cholesterol and triglyceride levels are also lowered, but findings are variable. Other health benefits, such as improved appetite regulation and favorable changes in the diversity of the gut microbiome, have also been demonstrated, but evidence for these effects is limited. Intermittent fasting is generally safe and does not result in energy level disturbances or increased disordered eating behaviors. In summary, intermittent fasting is a safe diet therapy that can produce clinically significant weight loss (>5%) and improve several markers of metabolic health in individuals with obesity.

Intermittent Fasting and Sleep: A Review of Human Trials

This review examines the effects of two popular intermittent fasting regimens on sleep in adults with overweight and obesity. Specifically, the effects of time restricted eating (TRE; eating all food within a 4-10 h window) and alternate day fasting (ADF; 600 kcal fast day alternated with ad libitum feast day) on sleep quality, sleep duration, sleep latency, sleep efficiency, insomnia severity, and risk of obstructive sleep apnea, will be summarized. The role of weight loss will also be discussed. Results from our review reveal that the majority of these trials produced weight loss in the range of 1-6% from baseline. Sleep quality and sleep duration remained unaltered with TRE and ADF, as assessed by the Pittsburgh Sleep Quality Index (PSQI). The effects of intermittent fasting on sleep latency and sleep efficiency are mixed, with one study showing worsening of these parameters, and others showing no effect. Insomnia severity and the risk of obstructive sleep apnea remained unchanged in the trials assessing these metrics. Taken together, these preliminary findings suggest that TRE and ADF produce mild to moderate weight loss (1-6%) but their effects on sleep remain unclear. Solid conclusions are difficult to establish since participants in the studies had healthy sleep durations and no clinical insomnia at baseline, leaving little room for improvement in these metrics. Moreover, none of the trials were adequately powered to detect statistically significant changes in any measure of sleep. Future well-powered trials, conducted in individuals with diagnosed sleep disturbances, will be necessary to elucidate the effect of these popular diets on sleep.

Time restricted eating for the prevention of type 2 diabetes

Type 2 diabetes can potentially be prevented by targeted lifestyle and weight loss interventions. Time restricted eating (TRE) is a form of intermittent fasting that has emerged as a novel diet strategy to reduce body weight and improve glycaemic control. TRE involves eating within a certain window of time (usually 4 to 10 h), and water-fasting for the remaining hours of the day. The purpose of this review is to summarize the effects of TRE on body weight and markers of glycaemic control in human subjects. We also aim to provide mechanistic insights into the effect of TRE on insulin sensitivity and glucose tolerance. Results to date reveal that TRE produces mild weight loss (1%-4% from baseline) and energy restriction, when food consumption is restricted to 4-10 h/day. TRE also reduces fasting insulin and improves insulin sensitivity in individuals with prediabetes and those with obesity. Moreover, TRE improves glucose tolerance and decreases serum glucose excursions. The possible mechanisms underlying these benefits include increased autophagic flux, mild elevations in ketone bodies, a reduction in oxidative stress, and the stimulation of β-cell responsiveness. While these preliminary results offer promise for the use of TRE in the prevention of type 2 diabetes, larger and longer-term human trials will be needed to confirm these findings.

Does the weight loss efficacy of alternate day fasting differ according to sex and menopausal status?

BACKGROUND AND AIMS

This study examined if the weight loss and metabolic benefits of alternate day fasting (ADF) varies according to sex and menopausal status in adults with obesity.

METHODS AND RESULTS

This secondary analysis pooled the data of men and women (n = 75) who participated in three 12-week ADF studies (500 kcal fast day; alternated with an ad libitum intake feast day). Body weight decreased in premenopausal women (-4.6 ± 3.2%), postmenopausal women (-6.5 ± 3.2%) and men (-6.2 ± 4.4%) (main effect of time, P < 0.001), with no difference between groups (no group × time interaction). Energy intake on fast days was higher than prescribed in all groups (∼400-500 excess kcal consumed), with no differences between groups. Fat mass, lean mass, fasting insulin, and insulin resistance, and blood pressure decreased similarly in all groups (main effect of time, P < 0.05 for all comparisons). LDL cholesterol decreased more in postmenopausal versus premenopausal women (group × time interaction, P = 0.01). Fasting glucose, HDL cholesterol, and triglycerides remained unchanged in all groups.

CONCLUSION

These findings suggest that the weight loss and metabolic benefits of ADF do not generally vary according to sex or menopausal status in adults with obesity.

TRIAL REGISTRATION

Clinicaltrials.gov, NCT00960505; NCT03528317.

Changes in subjective measures of appetite during 6 months of alternate day fasting with a low carbohydrate diet

OBJECTIVE

Alternate day fasting (ADF) has been shown to lower body weight and improve subjective appetite by increasing fullness. What remains unknown, however, is whether carbohydrate restriction during ADF would provide additional weight loss benefits by helping to lower hunger as well. Accordingly, this study examined the effect of 6-months of ADF combined with a low carbohydrate diet on fasting and postprandial appetite ratings.

METHODS

Adults with obesity (n = 31) participated in ADF (600 kcal "fast day" alternated with an ad libitum "feast day") with a low-carbohydrate background diet (30% carbohydrates, 35% protein, and 35% fat). The 6-month trial consisted of a 3-month weight loss period followed by a 3-month weight maintenance period.

RESULTS

After 6-months of an ADF-low carbohydrate diet, body weight decreased (P < 0.01) by 6.2 ± 1.0 kg, relative to baseline. Subjective hunger and fullness did not change throughout the study. Fasting insulin decreased (P < 0.05) by 3.3 ± 1.3 μlU/mL by month 6, relative to baseline. Fasting glucose and insulin resistance, remained unchanged over the course of the study. Hunger and fullness were not related to body weight, glucoregulatory factors or energy intake.

CONCLUSIONS

These findings suggest that ADF combined with a low carbohydrate diet is not associated with any changes in appetite, relative to baseline.

TRIAL REGISTRATION

Clinicaltrials.gov, NCT03528317.

Alternate Day Fasting Combined with a Low Carbohydrate Diet: Effect on Sleep Quality, Duration, Insomnia Severity and Risk of Obstructive Sleep Apnea in Adults with Obesity

Background: Alternate day fasting combined with a low carbohydrate diet (ADF-LC) is an effective weight loss regimen. Whether the weight loss induced by ADF-LC can improve sleep, remains unknown. Objective: This study examined the effect an ADF-LC diet on sleep quality, duration, insomnia severity and the risk of obstructive sleep apnea. Methods: Adults with obesity (n = 31) participated in ADF (600 kcal “fast day”; ad libitum intake “feast day”) with a low-carbohydrate diet (30% carbohydrates, 35% protein, and 35% fat). The 6-month trial consisted of a 3-month weight loss period followed by a 3-month weight maintenance period. Results: Reductions in body weight (−5 ± 1 kg, p < 0.001) and fat mass (−4 ± 1 kg, p < 0.01) were noted during the weight loss period, and these reductions were sustained during the weight maintenance period. Lean mass and visceral fat remained unchanged. The Pittsburgh Sleep Quality Index (PSQI) score indicated poor sleep quality at baseline (6.4 ± 0.7) with no change by month 3 or 6, versus baseline. ISI score indicated subthreshold insomnia at baseline (8.5 ± 1.0), with no change by month 3 or 6, versus baseline. The percent of subjects with high risk of obstructive sleep apnea at baseline was 45%, with no change by month 3 or 6. Wake time, bedtime, and sleep duration remained unchanged. Conclusion: The ADF-LC diet does not impact sleep quality, duration, insomnia severity or the risk of obstructive sleep apnea in adults with obesity.

Effects of 4- and 6-h Time-Restricted Feeding on Weight and Cardiometabolic Health: A Randomized Controlled Trial in Adults with Obesity

Time-restricted feeding (TRF) regimens have grown in popularity; however, very few studies have examined their weight-loss efficacy. We conducted the first human trial (Clinicaltrials.gov NCT03867773) to compare the effects of two popular forms of TRF (4 and 6 h) on body weight and cardiometabolic risk factors. Adults with obesity were randomized to 4-h TRF (eating only between 3 and 7 p.m.), 6-h TRF (eating only between 1 and 7 p.m.), or a control group (no meal timing restrictions). After 8 weeks, 4- and 6-h TRF produced comparable reductions in body weight (∼3%), insulin resistance, and oxidative stress, versus controls. Energy intake was reduced by ∼550 kcal/day in both TRF groups, without calorie counting. These findings suggest that 4- and 6-h TRF induce mild reductions in body weight over 8 weeks and show promise as interventions for weight loss. These diets may also improve some aspects of cardiometabolic health.

Changes in Body Weight in Relation to Appetite During 6 Months of Alternate Day Fasting with a Low Carbohydrate Diet

Objectives

Alternate day fasting (ADF) has been shown to lower body weight and improve subjective appetite by increasing fullness over time. What remains unknown, however, is whether carbohydrate restriction during ADF would provide additional weight loss benefits by helping to lower hunger as well. Accordingly, this study examined the effect of 6-months of ADF combined with a low carbohydrate diet on fasting and postprandial appetite ratings. The relationship between changes in appetite and body weight was also examined.

Methods

Adults with obesity (n = 31) participated in ADF (600 kcal “fast day” alternated with an ad libitum “feast day”) with a low-carbohydrate background diet (30% carbohydrates, 35% protein, and 35% fat). The 6-month trial consisted of a 3- month weight loss period followed by a 3-month weight maintenance period.

Results

Body weight (P &lt; 0.001) decreased by 5.5 ± 0.5% by month 3 (end of weight loss period) and by 6.3 ± 1.0% by month 6 (end of weight maintenance period). Subjective hunger and fullness did not change during the weight loss period, or the weight maintenance period. Hunger and fullness were not related to changes in body weight during the weight loss or weight maintenance periods. Fasting insulin decreased (P = 0.03) by − 24 ± 8% by month 6 relative to baseline. Fasting glucose and homeostatic model assessment of insulin resistance (HOMA-IR), remained unchanged over the course of the study.

Conclusions

These findings suggest that ADF combined with a low carbohydrate diet is an effective way of lowering body weight. However, these weight loss benefits are not related to improvements in hunger or fullness.

Funding Sources

Nestle Health Sciences.

The Effect of 6- h and 8-h Time Restricted Feeding on Body Weight, Glucoregulatory Factors, IGF-1 and IGFBP-3 in Adults with Obesity

Objectives

Time restricted feeding is a novel approach to intermittent fasting which includes a 6–10 hour feeding window and a 14–18 hour fasting window daily. Some forms of intermittent fasting have resulted in improvement in IGF-1 and IGFBP-3 in mice. These factors may affect cancer risk and cancer progression after diagnosis. However, effect in humans remains unknown. This exploratory analysis examined the effect of 12 weeks of 8-hour time-restricted feeding (10:00–18:00) and 8 weeks of 6-hour time-restricted feeding (12:00–18:00) versus a control in adults with obesity.

Methods

Participants with obesity (n = 24) participated in either an 8-h time restricted feeding intervention (ad libitum feeding between 10:00–6:00 pm) for 12 weeks or a 6-h time restricted feeding intervention (ad libitum feeding between 1:00–700 pm) for 8 weeks. Data for two time-restricted feeding trials were combined for this exploratory analysis and compared to a no intervention control group with obesity (n = 8). Weight loss, glucose regulatory factors, IGF-1 and IGFBP3 were measured.

Results

Body weight decreased significantly more in the 6-h (−2.82 ± 0.05 kg) and the 8-h (−2.77  ± 0.50 kg) groups than the controls (p &lt; 0.001). Fat mass decreased significantly more in the 6-h (−1.5 ± 0.2 kg) and the 8-h (−1.5 ± 0.4 kg) groups than the controls (p = 0.016).  Lean mass decreased significantly more in the 6-h group (−1.8 ± 0.2 kg) than the 8-h (p = .005) and the controls (p = .004). HOMA-IR decreased significantly more in the 8-h group (−0.3 ± 0.1 units) than the control group (p = 0.38). There was no difference in HOMA-IR (measure of insulin resistance) between the 6-h group (−.01 ±  0.3 units) and either the 8-h or the control groups (p = 0.91 and p = 0.86). Fasting insulin decreased significantly more in the 8-h group (−1.2 ± 0.6 uIU/ml) than control group (p = .033). There was no difference in change in insulin between the 8-h and 6-h groups (p = .952). No changes were seen in glucose, IGF-1 (8-h: −3.04 ± 13.49 ng/mL, 6-h: −0.42 ± 16.96 ng/mL) or IGFBP-3 (8-h: 0.17 ± 0.15 ng/mL, 6-h: 0.18 ± 0.07 ng/mL).

Conclusions

These findings suggest that 6-h and 8-h time-restricted feeding produce mild weight and fat loss as well as glucoregulatory improvement. It is unclear if time restricted feeding effects the cancer promoting biomarkers, IGF-1 and IGFBP3.

Funding Sources

University of Illinois at Chicago.

Effect of time restricted feeding on the gut microbiome in adults with obesity: A pilot study

BACKGROUND

Time restricted feeding is a form of intermittent fasting where participants shorten the daily window in which they eat.

AIM

This is the first study to examine the effects of intermittent fasting on changes in the gut microbiome.

METHODS

Adults with obesity (n = 14) participated in a daily 8-hour time restricted feeding intervention (8-hour feeding window/16-hour fasting window) for 12 weeks. Fecal microbiota were determined by 16 S rRNA (ribosomal ribonucleic acid) gene sequencing of stool samples.

RESULTS

Body weight decreased (P < 0.05) by -2 ± 1 kg. Gut microbiota phylogenetic diversity remained unchanged. The two most common phyla were Firmicutes and Bacteroidetes accounting for 61.2% and 26.9% of total abundance at baseline. No significant alterations in the abundance of Firmicutes, Bacteroidetes, or any other phyla were detected after 12 weeks of time restricted feeding.

CONCLUSIONS

Time restricted feeding did not significantly alter the diversity or overall composition of the gut microbiome.

Alternate day fasting combined with a low-carbohydrate diet for weight loss, weight maintenance, and metabolic disease risk reduction

OBJECTIVE

Alternate day fasting (ADF) is a popular weight loss regimen. Whether carbohydrate restriction can enhance the weight loss achieved with ADF remains unclear. Accordingly, this study examined the effect of ADF combined with a low-carbohydrate diet on body weight and metabolic disease risk factors.

METHODS

Adults with obesity (n = 31) participated in ADF (600 kcal "fast day" alternated with an ad libitum "feast day") with a low-carbohydrate background diet (30% carbohydrates, 35% protein, and 35% fat). The 6-month trial consisted of a 3-month weight loss period followed by a 3-month weight maintenance period.

RESULTS

Body weight decreased (-5.5 ± 0.5%; P < .001) during the weight loss period (month 0-3) but remained stable (P = .57) during the weight maintenance period (month 4-6). Net weight loss by month 6 was -6.3 ± 1.0%. Fat mass was reduced (P < .01) by month 6, while lean mass and visceral fat mass remained unchanged. Total cholesterol and low-density lipoprotein (LDL) cholesterol levels decreased (P < .05) by -6 ± 2% and - 8 ± 3%, respectively, by month 6. Systolic blood pressure was also reduced (P = .03) by -7 ± 3 mm Hg. Fasting insulin decreased (P = .03) by -24 ± 8% by month 6 relative to baseline. High-density lipoprotein (HDL) cholesterol, triglycerides, diastolic blood pressure, heart rate, fasting glucose, homeostatic model assessment of insulin resistance (HOMA-IR), and haemoglobin A1C (HbA1c) remained unchanged.

CONCLUSIONS

These findings suggest that ADF combined with a low-carbohydrate diet is effective for weight loss, weight maintenance, and improving certain metabolic disease risk factors such as LDL cholesterol, blood pressure, and fasting insulin. While these preliminary findings are promising, they still require confirmation by a randomized control trial.

Weight loss efficacy of alternate day fasting versus daily calorie restriction in subjects with subclinical hypothyroidism: a secondary analysis

This study compared the weight loss efficacy of alternate-day fasting (ADF) versus daily calorie restriction (CR) in adults with subclinical hypothyroidism. After 6 months, body weight decreased (P < 0.001) similarly by ADF (-7% ± 1%) and CR (-8% ± 2%). Insulin resistance decreased (P < 0.05) more by ADF versus CR. Free thyroxin and thyroid-stimulating hormone remained unchanged. Thus, ADF and CR produce similar weight loss in this population, without affecting thyroid hormone levels. Novelty Intermittent fasting and daily restriction produce similar reductions in body weight in subjects with subclinical hypothyroidism.

Beverage intake during alternate-day fasting: Relationship to energy intake and body weight

BACKGROUND

Alternate-day fasting (ADF) involves a 'famine day' (25% energy intake) and a 'feast day' (ad libitum intake). This secondary analysis examined changes in beverage intake in relation to energy intake and body weight during 12 months of ADF versus daily calorie restriction (CR).

METHODS

Obese subjects (n = 100 enrolled, n = 69 completers) were randomized to one of three groups for 12 months: (a) ADF; (b) CR; or (c) control.

RESULTS

At baseline, intakes of diet soda, caffeinated beverages, sugar-sweetened soda, alcohol, juice, and milk were similar between groups. There were no statistically significant changes in the intake of these beverages by month 6 or 12 between ADF (feast or famine day), CR, or control groups. Beverage intake was not related to energy intake or body weight at month 6 or 12 in any group.

CONCLUSION

These pilot findings suggest that intermittent fasting does not impact beverage intake in a way that affects energy intake or body weight.

Differential Effects of Alternate-Day Fasting Versus Daily Calorie Restriction on Insulin Resistance

OBJECTIVE

This study compared the effects of alternate-day fasting (ADF) with those of daily calorie restriction (CR) on body weight and glucoregulatory factors in adults with overweight or obesity and insulin resistance.

METHODS

This secondary analysis examined the data of insulin-resistant individuals (n = 43) who participated in a 12-month study that compared ADF (25% energy needs on "fast days"; 125% energy needs on alternating "feast days") with CR (75% energy needs every day) and a control group regimen.

RESULTS

In insulin-resistant participants, weight loss was not different between ADF (-8% ± 2%) and CR (-6% ± 1%) by month 12, relative to controls (P < 0.0001). Fat mass and BMI decreased (P < 0.05) similarly from ADF and CR. ADF produced greater decreases (P < 0.05) in fasting insulin (-52% ± 9%) and insulin resistance (-53% ± 9%) compared with CR (-14% ± 9%; -17% ± 11%) and the control regimen by month 12. Lean mass, visceral fat mass, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, triglycerides, blood pressure, C-reactive protein, tumor necrosis factor α, and interleukin 6 values remained unchanged.

CONCLUSIONS

These findings suggest that ADF may produce greater reductions in fasting insulin and insulin resistance compared with CR in insulin-resistant participants despite similar decreases in body weight.

Safety of 8-h Time Restricted Feeding in Adults with Obesity (FS18-05-19)

Objectives

Time restricted feeding (TRF) is a novel approach to intermittent fasting which includes a 4–10 hour feeding window and a 14–20 hour fasting window daily. However, the safety of TRF has yet to be determined. This study was undertaken to determine the effects of TRF on certain safety parameters, including: eating disorder symptoms, body image perception, complete blood count, resting metabolic rate, and frequency of adverse events, in adults with obesity.

Methods

Adults with obesity (n = 23) participated in an 8-h TRF intervention (ad libitum feeding between 10:00 to 18:00 h, water fasting between 18:00 to 10:00 h) for 12 weeks.

Results

Body weight significantly (P < 0.001) decreased by 2.6 ± 0.5% after 12 weeks of TRF. Resting metabolic rate did not change over time (baseline: 1431 ± 62 kcal/d; week 1: 1393 ± 82 kcal/d; week 12: 1318 ± 61 kcal/d). Self-reported adverse events (gastrointestinal or neurological) did not change over time. Eating disorder symptoms including depression, binge eating, purgative behavior, fear of fatness, restrictive eating, and avoidance of forbidden foods, did not change from baseline to week 12. Concerns about body size and shape remained unchanged. Cognitive restraint, uncontrolled eating and emotional eating did not change over time. There were no significant changes in any of the complete blood count parameters from baseline to week 12.

Conclusions

This study is the first to show that TRF is a safe diet therapy for weight loss as it does not negatively impact eating disorder symptoms, eating behaviors, resting metabolic rate, or measures of overall health, such as complete blood count.

Funding Sources

University of Illinois Chicago Campus Research Board Pilot Grant; NIH T32HL007909.

Effect of 8-h time-restricted feeding on sleep quality and duration in adults with obesity

This study examined the effects of time-restricted feeding (TRF; 8-h feeding window/16-h fasting window daily) on sleep. Obese adults (n = 23) followed 8-h TRF for 12 weeks. Pittsburgh Sleep Quality Index (PSQI) total score was below 5 at week 1 (4.7 ± 0.5) and week 12 (4.8 ± 0.7), indicating good sleep quality throughout the trial. Subjective measures of wake time, bedtime, and sleep duration remained unchanged. Findings from this secondary analysis indicate that TRF does not alter sleep quality or duration in subjects with obesity. Novelty This study is the first to show that TRF (8-h feeding window/16-h fasting window daily) does not alter sleep quality or duration in subjects with obesity.

Safety of 8-h time restricted feeding in adults with obesity

This study examines the safety of time restricted feeding (TRF; 8-h feeding window/16-h fasting window daily) in obese adults. Twenty-three subjects participated in an 8-h TRF intervention for 12 weeks. Self-reported adverse events, body image perception, complete blood count, and disordered eating patterns did not change from baseline to week 12. These findings suggest that consuming food within an 8-h window can safely facilitate weight loss in subjects with obesity.

Effects of 8-hour time restricted feeding on body weight and metabolic disease risk factors in obese adults: A pilot study

BACKGROUND:

Time restricted feeding decreases energy intake without calorie counting and may be a viable option for weight loss. However, the effect of this diet on body weight in obese subjects has never been examined.

OBJECTIVE:

This study investigated the effects of 8-h time restricted feeding on body weight and metabolic disease risk factors in obese adults.

DESIGN:

Obese subjects (n = 23) participated in an 8-h time restricted feeding intervention (ad libitum feeding between 10:00 to 18:00 h, water fasting between 18:00 to 10:00 h) for 12 weeks. Weight loss and other outcomes were compared to a matched historical control group (n = 23).

RESULTS:

Body weight and energy intake decreased in the time restricted group (–2.6% ± 0.5; –341 ± 53 kcal/d) relative to controls over 12 weeks (P < 0.05). Systolic blood pressure decreased in the time restricted feeding group (–7 ± 2 mm Hg) versus controls (P < 0.05). Fat mass, lean mass, visceral fat mass, diastolic blood pressure, LDL cholesterol, HDL cholesterol, triglycerides, fasting glucose, fasting insulin, HOMA-IR, and homocysteine were not significantly different from controls after 12 weeks (no group×time interaction).

CONCLUSION:

These findings suggest that 8-h time restricted feeding produces mild caloric restriction and weight loss, without calorie counting. It may also offer clinical benefits by reducing blood pressure.

Eating behavior traits of successful weight losers during 12 months of alternate-day fasting: An exploratory analysis of a randomized controlled trial

BACKGROUND

Alternate-day fasting (ADF) has gained popularity in recent years. The diet consists of a "fast day" where an individual consumes 0-25% of their energy needs, alternated with a "feast day" where a person is permitted to eat ad libitum.

AIM

This study examined eating behavior traits of successful weight losers during alternate day fasting.

METHODS

Obese participants ( n = 34) took part in 12 months of ADF and were grouped into a high (≥5%) or low-weight-loss (<5%) group post-treatment.

RESULTS

The high-weight-loss group demonstrated increased ( p = 0.04) fullness, decreased ( p = 0.03) hunger, increased dietary protein intake (15% to 20% of kcal, p = 0.04), and better adherence to fast-day calorie goals.

CONCLUSIONS

Thus, individuals who achieve clinically significant weight loss with ADF demonstrate improved satiety, increased protein intake, and better adherence to fast-day calorie goals.

Effect of alternate day fasting on markers of bone metabolism: An exploratory analysis of a 6-month randomized controlled trial

BACKGROUND

Alternate day fasting (ADF) is a novel diet therapy that reduces body weight, but its effect on bone health remains unknown.

OBJECTIVE

This study examined the impact of ADF versus traditional daily calorie restriction (CR) on markers of bone metabolism in a 6-month randomized controlled trial.

METHODS

Overweight and obese subjects (n = 100) were randomized to 1 of 3 groups for 6 months: 1) ADF (25% energy intake fast day, alternated with 125% intake feast day; 2) CR (75% intake every day); or 3) control (usual intake every day).

RESULTS

Body weight decreased similarly (P < 0.001) by ADF (-7.8±1.2%) and CR (-8.8±1.5%), relative to controls by month 6. Lean mass, total body bone mineral content and total body bone mineral density remained unchanged in all groups. Circulating osteocalcin, bone alkaline phosphatase, and C-terminal telopeptide type I collagen (CTX) did not change in any group. IGF-1 increased (P < 0.01) in the CR group, with no change in the ADF or control group. When the data were sub-analyzed according to menopausal status, there were no differences between premenopausal or postmenopausal women for any marker of bone metabolism.

CONCLUSION

These findings suggest that 6 months of ADF does not have any deleterious impact on markers of bone metabolism in obese adults with moderate weight loss.

Effect of Alternate-Day Fasting on Weight Loss, Weight Maintenance, and Cardioprotection Among Metabolically Healthy Obese Adults: A Randomized Clinical Trial

IMPORTANCE

Alternate-day fasting has become increasingly popular, yet, to date, no long-term randomized clinical trials have evaluated its efficacy.

OBJECTIVE

To compare the effects of alternate-day fasting vs daily calorie restriction on weight loss, weight maintenance, and risk indicators for cardiovascular disease.

DESIGN, SETTING, AND PARTICIPANTS

A single-center randomized clinical trial of obese adults (18 to 64 years of age; mean body mass index, 34) was conducted between October 1, 2011, and January 15, 2015, at an academic institution in Chicago, Illinois.

INTERVENTIONS

Participants were randomized to 1 of 3 groups for 1 year: alternate-day fasting (25% of energy needs on fast days; 125% of energy needs on alternating "feast days"), calorie restriction (75% of energy needs every day), or a no-intervention control. The trial involved a 6-month weight-loss phase followed by a 6-month weight-maintenance phase.

MAIN OUTCOMES AND MEASURES

The primary outcome was change in body weight. Secondary outcomes were adherence to the dietary intervention and risk indicators for cardiovascular disease.

RESULTS

Among the 100 participants (86 women and 14 men; mean [SD] age, 44 [11] years), the dropout rate was highest in the alternate-day fasting group (13 of 34 [38%]), vs the daily calorie restriction group (10 of 35 [29%]) and control group (8 of 31 [26%]). Mean weight loss was similar for participants in the alternate-day fasting group and those in the daily calorie restriction group at month 6 (-6.8% [95% CI, -9.1% to -4.5%] vs -6.8% [95% CI, -9.1% to -4.6%]) and month 12 (-6.0% [95% CI, -8.5% to -3.6%] vs -5.3% [95% CI, -7.6% to -3.0%]) relative to those in the control group. Participants in the alternate-day fasting group ate more than prescribed on fast days, and less than prescribed on feast days, while those in the daily calorie restriction group generally met their prescribed energy goals. There were no significant differences between the intervention groups in blood pressure, heart rate, triglycerides, fasting glucose, fasting insulin, insulin resistance, C-reactive protein, or homocysteine concentrations at month 6 or 12. Mean high-density lipoprotein cholesterol levels at month 6 significantly increased among the participants in the alternate-day fasting group (6.2 mg/dL [95% CI, 0.1-12.4 mg/dL]), but not at month 12 (1.0 mg/dL [95% CI, -5.9 to 7.8 mg/dL]), relative to those in the daily calorie restriction group. Mean low-density lipoprotein cholesterol levels were significantly elevated by month 12 among the participants in the alternate-day fasting group (11.5 mg/dL [95% CI, 1.9-21.1 mg/dL]) compared with those in the daily calorie restriction group.

CONCLUSIONS AND RELEVANCE

Alternate-day fasting did not produce superior adherence, weight loss, weight maintenance, or cardioprotection vs daily calorie restriction.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00960505.

Changes in hunger and fullness in relation to gut peptides before and after 8 weeks of alternate day fasting

BACKGROUND & AIMS

Alternate day fasting (ADF; 25% energy intake "fast day", alternated with an ad libitum intake "feed day") is effective for weight loss. Whether or not ADF modulates hunger, fullness and gut peptides in a way that enhances dietary compliance and weight loss, remains unknown. Accordingly, this study examined the effect of ADF on postprandial appetite ratings and gut peptides.

METHODS

Obese subjects (n = 59) participated in an 8-week ADF protocol where food was provided on the fast day.

RESULTS

Body weight decreased (P < 0.0001) by 3.9 ± 0.6 kg after 8 weeks of diet. Reductions (P < 0.05) in fat mass (-2.2 ± 0.2 kg), fat free mass (-1.4 ± 0.2 kg), visceral fat mass (-0.1 ± 0.1 kg), and resting metabolic rate (RMR; -104 ± 28 kcal/day) were also observed. Fasting leptin and insulin decreased (P < 0.05), while AUC ghrelin levels increased (P < 0.05). Despite these metabolic changes, there was no increase in subjective hunger by the end of the study. Furthermore, fullness and PYY increased (P < 0.05). Fat free mass and RMR were not related to hunger or ghrelin at any time point.

CONCLUSION

These findings suggest that the absence of a compensatory increase in hunger in conjunction with an increase in sensations of fullness may contribute to the weight loss efficacy of an 8-week ADF regimen.

Modifiable lifestyle factors affecting bone health using calcaneus quantitative ultrasound in adolescent girls

One hundred and fourteen girls were measured for calcaneus QUS (stiffness index score), calcium intake, weight, and total hours spent in physical activity (moderate to high-impact activities and low to no-impact activities). Multiple regression analysis indicated that hours spent in moderate to high-impact activities, current calcium intake, and weight significantly predicted SI.

INTRODUCTION

To determine the influence of modifiable lifestyle factors on adolescent girls' bone health measured by calcaneus quantitative ultrasound (QUS).

METHODS

One hundred and fourteen girls, ages 14-18 (15.97 +/- .7), enrolled in high school physical education classes, were measured for calcaneus QUS (stiffness index score), height, weight, current calcium intake from 2-3 day food records, and estimated total hours spent in physical activity from kindergarten to present. Cumulative physical activity hours were separated into two classifications (according to their estimated strain from ground reaction force): moderate to high-impact activities and low to no-impact activities.

RESULTS

Pearson correlations between stiffness index (SI) and age, height, weight, current calcium intake, and hours spent in moderate to high-impact versus low to no-impact activities indicated a positive relationships between SI and weight (r = .259, p = .005), current calcium intake (r = .286, p = .002), and hours spent in moderate to high-impact activities (r = .451, p < .001). Multiple regression between SI and the above independent variables indicated that collectively, hours spent in moderate to high-impact activities, current calcium intake, and weight (r (2) = .363, p = <.001) significantly predicted SI.

CONCLUSION

Our data indicate that moderate to high-impact activities, current calcium intake, and weight positively influence bone properties of the calcaneus in adolescent girls.

Reported adoption of dietary fat and fiber recommendations among consumers

OBJECTIVE

To identify constraints in adopting dietary fat and fiber recommendations.

DESIGN

A questionnaire was mailed to a sample of the general population, a convenience sample of persons with heart disease and cancer in 11 states, and registered dietitians in 5 states. The survey included questions on demographic and attitudinal factors that were correlated with specific practices to reduce fat intake and increase fiber intake.

SETTING

From the general population sample of 6,206 eligible respondents (return rate of 51.5%), those selected were respondents who indicated that they would adopt a dietary recommendation if it were good for them (n = 2,682). Subsamples from the general population were matched to 362 registered dietitians and 147 persons with cancer or heart disease on selected demographic variables. Factors associated with adoption of specific behaviors were identified.

STATISTICAL ANALYSIS PERFORMED

Statistical analysis included chi 2, factor analysis, and analysis of variance.

RESULTS

The majority of persons who said they would adopt a fat-reducing behavior if it were good for their health reported practicing that behavior often or usually. More than 60% reported consuming whole grains; however, only 15% reported eating fruits and vegetables frequently. Among the general population sample, those more likely to practice a behavior had the following characteristics: female, college educated, older than 60 years, white, higher income, no children younger than 18 years, perceived health status as excellent, and absence of chronic disease. Registered dietitians and those with chronic disease were also more likely to follow dietary fat and fiber recommendations.

APPLICATIONS

Nutrition education messages that lead to increased consumption of dietary fiber need to be developed. Nutrition educators should provide strategies for consumers for increasing use of fruits and vegetables in all meals. Good taste and convenience are critical components. The food industry may assist by providing a wider array of convenience entrees or side dishes that feature produce and whole grains.

A stage-of-change classification system based on actions and beliefs regarding dietary fat and fiber

PURPOSE

The objectives of this study were to develop a stage-of-change classification system and to determine the degree to which various adult subgroups have adopted the behavioral changes necessary to achieve a low-fat and/or high-fiber diet as recommended by the Dietary Guidelines for Americans.

DESIGN

The study used a mail survey randomly sent to 7110 adults.

SETTING

The survey was conducted in 11 states and the District of Columbia.

SUBJECTS

The random sample included males and females over age 18. Of the eligible respondents, 3198 (51.5%) were included in this analysis, with 2004 and 2066 unambiguously classified into stages of change for fat and fiber, respectively.

MEASURES

Stage of change was defined by an algorithm based on self-reported intent and behaviors to limit fat and/or increase fiber.

RESULTS

45% of the respondents were classified as being in action/maintenance for fat and 38% for fiber. Women, older adults, individuals with advanced education, persons with diet-related chronic disease, people with higher levels of relevant nutrition knowledge and attitudes, and persons who indicated that health concerns were a primary influence on their diet were more likely to be in action/maintenance than other respondents.

CONCLUSIONS

The algorithm in this study presents a model that more closely reflects the proportions of the adult population that have achieved low-fat diets and classifies a greater proportion in the preparation stage than classification systems in previous studies.

Ultrafast semiconductor laser-diode-seeded Cr:LiSAF regenerative amplifier system

An ultrafast, hybrid mode-locked semiconductor laser-diode system has been used to seed a flash-lamp-pumped Cr:LiSAF regenerative amplifier system, producing subpicosecond pulses with millijoule output pulse energy. This system has the potential to eliminate argon-ion-pumped-based, ultrafast laser systems.

X-ray focusing with lobster-eye optics: a comparison of theory with experiment

We report an experimental investigation and comparison with simulation of the x-ray focusing of a flat, square profile microchannel plate. We use x rays with an energy of ~1.5 keV from a laser-produced plasma. The images were recorded with x-ray film. We find the focal structure to be consistent with theoretical expectations. The angular resolution of the focus is 0.96 mrad, which is a major improvement over previous results. The measured peak intensity gain is 27 ± 4, which is ~33% of that for a perfect optic.

Source characterization for x-ray proximity lithography

Calibrated x-ray spectra from laser-produced plasmas of materials with atomic numbers varying between 12 (Mg) and 83 (Bi) were recorded to optimize the conversion efficiency for proximity lithography in a 0.5-nm band centered at 1 nm. The highest efficiency (~0.8%) was found for L-shell emitters such as Cu ando M-shell emitters such as Ba. First-order debris measurements were carried out by measurement of the layer thickness deposited on witness plates 2 cm away from the target. Layers of 30-nm thickness were deposited in a single laser shot with Au and W targets.

Reoperation: cardiac surgery

The subject of cardiac reoperation in general has been infrequently discussed in the medical literature and has not yet appeared in the nursing literature. Yet reoperation presents a real challenge, accentuating some problems that are also associated with primary cases and posing some considerations that are unique to the reoperative situation. The objectives of this article are to discuss the reasons prompting reoperation for coronary revascularization, identify technical problems associated with reoperative coronary artery surgery, explore potential avenues for decreasing the need for reoperation, and discuss potential patient care problems in the immediate postoperative critical care setting.