Higher protein diet for weight management in young overweight women: a 12-month randomized controlled trial

Long Term Weight Loss Diets and Obesity Indices: Results of a Network Meta-Analysis

Background

Scientists have been investigating efficient interventions to prevent and manage obesity. This network meta-analysis (NMA) compared the effect of different diets [moderate macronutrients (MMs), low fat/high carbohydrate (LFHC), high fat/low carbohydrate (HFLC), and usual diet (UD)] on weight, body mass index (BMI), and waist circumference (WC) changes at ≥12 months.

Methods

We searched Medline, Embase, PubMed databases, and the Cochrane Library. We systematically assessed randomized controlled trials (RCTs) evaluating dietary interventions on adults (mean BMI ≥ 25 kg/m²) receiving active dietary counseling for ≥12 months. We pooled the data using a random-effect NMA. We assessed the quality of the included RCTs using the Cochrane risk of bias (ROB) tool.

Results

We included 36 trials, 14 of which compared HFLC with MM diets. Compared with UD, all diets were associated with a significant weight loss (WL) at ≥12 months, HFLC [mean difference in kg (95% CI): −5.5 (−7.6; −3.4)], LFHC [−5.0 (−7.1; −2.9)] and MM [−4.7 (−6.8; −2.7)]. HFLC, compared with MM diet, was associated with a slightly higher WL (of −0.77 kg) and drop in BMI (of −0.36 kg/m²), while no significant difference was detected in other dietary comparisons. WC was lower with all diets compared to UD, with no significant difference across specific diets. There was no significant interaction of the results with the pre-specified sub-groups. The ROB was moderate to high, mostly related to unclear allocation concealment, high dropout rate and unclear or lack of blinding of participants, providers, and outcome assessors.

Conclusion

Dietary interventions extending over ≥12 months are superior to UD in inducing weight, BMI and WC loss. HFLC might be associated with a slightly higher WL compared with MM diets.

Systematic Trial Registration

https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=103116, PROSPERO (CRD42018103116).

Low-carbohydrate versus balanced-carbohydrate diets for reducing weight and cardiovascular risk

BACKGROUND

Debates on effective and safe diets for managing obesity in adults are ongoing. Low-carbohydrate weight-reducing diets (also known as 'low-carb diets') continue to be widely promoted, marketed and commercialised as being more effective for weight loss, and healthier, than 'balanced'-carbohydrate weight-reducing diets.

OBJECTIVES

To compare the effects of low-carbohydrate weight-reducing diets to weight-reducing diets with balanced ranges of carbohydrates, in relation to changes in weight and cardiovascular risk, in overweight and obese adults without and with type 2 diabetes mellitus (T2DM).

SEARCH METHODS

We searched MEDLINE (PubMed), Embase (Ovid), the Cochrane Central Register of Controlled Trials (CENTRAL), Web of Science Core Collection (Clarivate Analytics), ClinicalTrials.gov and WHO International Clinical Trials Registry Platform (ICTRP) up to 25 June 2021, and screened reference lists of included trials and relevant systematic reviews. Language or publication restrictions were not applied.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) in adults (18 years+) who were overweight or living with obesity, without or with T2DM, and without or with cardiovascular conditions or risk factors. Trials had to compare low-carbohydrate weight-reducing diets to balanced-carbohydrate (45% to 65% of total energy (TE)) weight-reducing diets, have a weight-reducing phase of 2 weeks or longer and be explicitly implemented for the primary purpose of reducing weight, with or without advice to restrict energy intake.  DATA COLLECTION AND ANALYSIS: Two review authors independently screened titles and abstracts and full-text articles to determine eligibility; and independently extracted data, assessed risk of bias using RoB 2 and assessed the certainty of the evidence using GRADE. We stratified analyses by participants without and with T2DM, and by diets with weight-reducing phases only and those with weight-reducing phases followed by weight-maintenance phases. Primary outcomes were change in body weight (kg) and the number of participants per group with weight loss of at least 5%, assessed at short- (three months to < 12 months) and long-term (≥ 12 months) follow-up.

MAIN RESULTS

We included 61 parallel-arm RCTs that randomised 6925 participants to either low-carbohydrate or balanced-carbohydrate weight-reducing diets. All trials were conducted in high-income countries except for one in China. Most participants (n = 5118 randomised) did not have T2DM. Mean baseline weight across trials was 95 kg (range 66 to 132 kg). Participants with T2DM were older (mean 57 years, range 50 to 65) than those without T2DM (mean 45 years, range 22 to 62). Most trials included men and women (42/61; 3/19 men only; 16/19 women only), and people without baseline cardiovascular conditions, risk factors or events (36/61). Mean baseline diastolic blood pressure (DBP) and low-density lipoprotein (LDL) cholesterol across trials were within normal ranges. The longest weight-reducing phase of diets was two years in participants without and with T2DM. Evidence from studies with weight-reducing phases followed by weight-maintenance phases was limited. Most trials investigated low-carbohydrate diets (> 50 g to 150 g per day or < 45% of TE; n = 42), followed by very low (≤ 50 g per day or < 10% of TE; n = 14), and then incremental increases from very low to low (n = 5). The most common diets compared were low-carbohydrate, balanced-fat (20 to 35% of TE) and high-protein (> 20% of TE) treatment diets versus control diets balanced for the three macronutrients (24/61). In most trials (45/61) the energy prescription or approach used to restrict energy intake was similar in both groups. We assessed the overall risk of bias of outcomes across trials as predominantly high, mostly from bias due to missing outcome data. Using GRADE, we assessed the certainty of evidence as moderate to very low across outcomes.  Participants without and with T2DM lost weight when following weight-reducing phases of both diets at the short (range: 12.2 to 0.33 kg) and long term (range: 13.1 to 1.7 kg).  In overweight and obese participants without T2DM: low-carbohydrate weight-reducing diets compared to balanced-carbohydrate weight-reducing diets (weight-reducing phases only) probably result in little to no difference in change in body weight over three to 8.5 months (mean difference (MD) -1.07 kg, (95% confidence interval (CI) -1.55 to -0.59, I2 = 51%, 3286 participants, 37 RCTs, moderate-certainty evidence) and over one to two years (MD -0.93 kg, 95% CI -1.81 to -0.04, I2 = 40%, 1805 participants, 14 RCTs, moderate-certainty evidence); as well as change in DBP and LDL cholesterol over one to two years. The evidence is very uncertain about whether there is a difference in the number of participants per group with weight loss of at least 5% at one year (risk ratio (RR) 1.11, 95% CI 0.94 to 1.31, I2 = 17%, 137 participants, 2 RCTs, very low-certainty evidence).  In overweight and obese participants with T2DM: low-carbohydrate weight-reducing diets compared to balanced-carbohydrate weight-reducing diets (weight-reducing phases only) probably result in little to no difference in change in body weight over three to six months (MD -1.26 kg, 95% CI -2.44 to -0.09, I2 = 47%, 1114 participants, 14 RCTs, moderate-certainty evidence) and over one to two years (MD -0.33 kg, 95% CI -2.13 to 1.46, I2 = 10%, 813 participants, 7 RCTs, moderate-certainty evidence); as well in change in DBP, HbA1c and LDL cholesterol over 1 to 2 years. The evidence is very uncertain about whether there is a difference in the number of participants per group with weight loss of at least 5% at one to two years (RR 0.90, 95% CI 0.68 to 1.20, I2 = 0%, 106 participants, 2 RCTs, very low-certainty evidence).  Evidence on participant-reported adverse effects was limited, and we could not draw any conclusions about these.  AUTHORS' CONCLUSIONS: There is probably little to no difference in weight reduction and changes in cardiovascular risk factors up to two years' follow-up, when overweight and obese participants without and with T2DM are randomised to either low-carbohydrate or balanced-carbohydrate weight-reducing diets.

Are Dietary Proteins the Key to Successful Body Weight Management? A Systematic Review and Meta-Analysis of Studies Assessing Body Weight Outcomes after Interventions with Increased Dietary Protein

The primary aim was to systematically review the current evidence investigating if dietary interventions rich in protein lead to improved body weight management in adults with excessive body weight. The secondary aim was to investigate potential modifying effects of phenotyping. A systematic literature search in PubMed, Web of Science, and Cochrane Library identified 375 randomized controlled trials with 43 unique trials meeting the inclusion criteria. The Cochrane collaboration tool was used for a thorough risk of bias assessment. Based on 37 studies evaluating effects of dietary protein on body weight, the participants with increased protein intake (ranging from 18–59 energy percentage [E%]) were found to reduce body weight by 1.6 (1.2; 2.0) kg (mean [95% confidence interval]) compared to controls (isocaloric interventions with energy reduction introduced in certain studies). Individuals with prediabetes were found to benefit more from a diet high in protein compared to individuals with normoglycemia, as did individuals without the obesity risk allele (AA genotype) compared to individuals with the obesity risk alleles (AG and GG genotypes). Thus, diets rich in protein would seem to have a moderate beneficial effect on body weight management.

Is protein the forgotten ingredient: Effects of higher compared to lower protein diets on cardiometabolic risk factors. A systematic review and meta-analysis of randomised controlled trials

BACKGROUND AND AIMS

Higher protein (HP) diets may lead to lower cardiometabolic risk, compared to lower protein (LP) diets. This systematic review and meta-analysis aims to investigate the effects of HP versus LP diets on cardiometabolic risk factors in adults, using the totality of the current evidence from randomised controlled trials (RCTs).

METHODS

Systematic searches were conducted in electronic databases, up to November 2020. Random effects meta-analyses were conducted to pool the standardised mean differences (SMD) and 95% confidence intervals (CI). The main outcomes were weight loss, body mass index (BMI), waist circumference, fat mass, systolic and diastolic BP, total cholesterol, HDL-and LDL-cholesterol, triacylglycerol, fasting glucose and insulin, and glycated haemoglobin.

RESULTS

Fifty-seven articles reporting on 54 RCTs were included, involving 4344 participants (65% female, mean age: 46 (SD 10) years, mean BMI: 33 (SD 3) kg/m²), with a mean study duration of 18 weeks (range: 4 to 156 weeks). Compared to LP diets (range protein (E%):10-23%), HP diets (range protein (E%): 20-45%) led to more weight loss (SMD -0.13, 95% CI: -0.23, -0.03), greater reductions in fat mass (SMD -0.14, 95% CI: -0.24, -0.04), systolic BP (SMD -0.12, 95% CI: -0.21, -0.02), total cholesterol (SMD -0.11, 95% CI: -0.19, -0.02), triacylglycerol (SMD -0.22, 95% CI: -0.30, -0.14) and insulin (SMD -0.12, 95% CI: -0.22, -0.03). No significant differences were observed for the other outcomes.

CONCLUSIONS

Higher protein diets showed small, but favourable effects on weight loss, fat mass loss, systolic blood pressure, some lipid outcomes and insulin, compared to lower protein diets.

Can diet-induced weight loss improve iron homoeostasis in patients with obesity: A systematic review and meta-analysis

Despite the increasing worldwide prevalence of obesity and iron deficiency (ID), there are still no guidelines on how to treat and manage obesity-related ID. The aim of this systematic review and meta-analysis was to investigate whether weight loss can re-establish iron homoeostasis among subjects with unhealthy weight (overweight [OW] or obesity). PubMed, Medline, Embase, Web of Science, and the Cochrane Library were systemically searched for studies that compared the iron status before and after a weight-loss intervention. A random-effects model was used to calculate the pooled and subgroup weighted mean differences (WMDs) of iron biomarkers. In total, 879 subjects were pooled across 14 studies. Improved haemoglobin was found in longitudinal studies (WMD = 2.50 g/dl, 95% confidence interval [CI]: 0.88, 4.12 g/dl, I² = 14%) but not in randomized controlled trials or after being stratified by dietary programmes. Significantly increased transferrin saturation was observed in pooled (WMD = 1.68%, 95% CI: 0.97%, 2.39%, I² = 44%) and subgroup analyses. A meta-regression showed that changes in the iron status were positively correlated with changes in the body mass index (BMI) and the intervention duration but negatively correlated with the baseline body weight/BMI, age, gender and a standard hypocaloric diet. Our data suggested that in spite of energy restrictions, weight loss may help re-establish iron homoeostasis in people who are OW or obese.

Whey Protein Drink Ingestion before Breakfast Suppressed Energy Intake at Breakfast and Lunch, but Not during Dinner, and Was Less Suppressed in Healthy Older than Younger Men

Ageing is associated with changes in feeding behavior. We have reported that there is suppression of energy intake three hours after whey protein drink ingestion in young, but not older, men. This study aimed to determine these effects over a time period of 9 h. Fifteen younger (27 ± 1 years, 25.8 ± 0.7 kg/m²) and 15 older (75 ± 2 years, 26.6 ± 0.8 kg/m²) healthy men were studied on three occasions on which they received, in a randomized order, a 30 g/120 kcal, 70 g/280 kcal whey-protein, or control (~2 kcal) drink. Ad-libitum energy intake (sum of breakfast, lunch, and dinner) was suppressed in a protein load responsive fashion (P = 0.001). Suppression was minimal at breakfast, substantial at lunch (~-16%, P = 0.001), no longer present by dinner, and was less in older than younger men (-3 ± 4% vs. -8 ± 4%, P = 0.027). Cumulative protein intake was increased in the younger and older men (+20% and +42%, P < 0.001). Visual analogue scale ratings of fullness were higher and desire to eat and prospective food consumption were lower after protein vs. control, and these effects were smaller in older vs. younger men (interaction effect P < 0.05). These findings support the use of whey-protein drink supplements in older people who aim to increase their protein intake without decreasing their overall energy intake.

Effect of Lower Versus Higher Red Meat Intake on Cardiometabolic and Cancer Outcomes: A Systematic Review of Randomized Trials

This article has been corrected. The original version (PDF) is appended to this article as a Supplement.

BACKGROUND

Few randomized trials have evaluated the effect of reducing red meat intake on clinically important outcomes.

PURPOSE

To summarize the effect of lower versus higher red meat intake on the incidence of cardiometabolic and cancer outcomes in adults.

DATA SOURCES

EMBASE, CENTRAL, CINAHL, Web of Science, and ProQuest from inception to July 2018 and MEDLINE from inception to April 2019, without language restrictions.

STUDY SELECTION

Randomized trials (published in any language) comparing diets lower in red meat with diets higher in red meat that differed by a gradient of at least 1 serving per week for 6 months or more.

DATA EXTRACTION

Teams of 2 reviewers independently extracted data and assessed the risk of bias and the certainty of the evidence.

DATA SYNTHESIS

Of 12 eligible trials, a single trial enrolling 48 835 women provided the most credible, though still low-certainty, evidence that diets lower in red meat may have little or no effect on all-cause mortality (hazard ratio [HR], 0.99 [95% CI, 0.95 to 1.03]), cardiovascular mortality (HR, 0.98 [CI, 0.91 to 1.06]), and cardiovascular disease (HR, 0.99 [CI, 0.94 to 1.05]). That trial also provided low- to very-low-certainty evidence that diets lower in red meat may have little or no effect on total cancer mortality (HR, 0.95 [CI, 0.89 to 1.01]) and the incidence of cancer, including colorectal cancer (HR, 1.04 [CI, 0.90 to 1.20]) and breast cancer (HR, 0.97 [0.90 to 1.04]).

LIMITATIONS

There were few trials, most addressing only surrogate outcomes, with heterogeneous comparators and small gradients in red meat consumption between lower versus higher intake groups.

CONCLUSION

Low- to very-low-certainty evidence suggests that diets restricted in red meat may have little or no effect on major cardiometabolic outcomes and cancer mortality and incidence.

PRIMARY FUNDING SOURCE

None (PROSPERO: CRD42017074074).

Tree Nut Consumption and Adipose Tissue Mass: Mechanisms of Action

There is concern that tree nuts may cause weight gain due to their energy density, yet evidence shows that tree nuts do not adversely affect weight status. Epidemiologic and experimental studies have shown a reduced risk of chronic diseases with tree nut consumption without an increased risk of weight gain. In fact, tree nuts may protect against weight gain and benefit weight-loss interventions. However, the relation between tree nut consumption and adiposity is not well understood at the mechanistic level. This review summarizes the proposed underlying mechanisms that might account for this relation. Evidence suggests that tree nuts may affect adiposity through appetite control, displacement of unfavorable nutrients, increased diet-induced thermogenesis, availability of metabolizable energy, antiobesity action of bioactive compounds, and improved functionality of the gut microbiome. The gut microbiome is a common factor among these mechanisms and may mediate, in part, the relation between tree nut consumption and reduced adiposity. Further research is needed to understand the impact of tree nuts on the gut microbiome and how the gut microbial environment affects the nutrient absorption and metabolism of tree nuts. The evidence to date suggests that tree nut consumption favorably affects body composition through different mechanisms that involve the gut microbiome. A better understanding of these mechanisms will contribute to the evolving science base that addresses the causes and treatments for overweight and obesity.

Fit4YAMs: Structuring a Lifestyle Intervention for Rural Overweight and Obese Young Adult Males Using Participatory Design

PURPOSE

Young adult males (YAMs) are understudied with respect to lifestyle interventions to address overweight and obesity in this group. This study reports on the participatory design of the structure and delivery of the Fit4YAMs text message-based lifestyle intervention for 18- to 25-year-old rural YAMs in Australia.

METHODS

Two semi-structured focus group discussions were held with six overweight or obese YAMs. Sessions explored their preferences for the structure and delivery of a weight loss intervention. Focus groups were recorded, and the contents transcribed verbatim for thematic analysis.

RESULTS

The YAMs were unanimous in their preference for a highly personalized intervention program, complete with personalized goal setting, personalized motivation and engagement strategies, and personalized text message content. A text message frequency of three-four messages per week was deemed optimal for this group. Minimal direct contact by the intervention team was requested, but with clear guidelines and reminders of key contacts whom they could contact should they require help and guidance. The YAMs also agreed that a comprehensive goal setting session and personalization session prior to commencement of the intervention would be best.

CONCLUSIONS

To engage rural YAMs in lifestyle interventions, a high degree of personalization of the program appears important. Although initially more time and resource intensive than a less personalized approach, it is essential to identify strategies to prevent and reverse weight gain in this hard to engage group. Maximizing their engagement using a more personalized approach could be the key to promoting long-term health outcomes in this group.

Dietary Protein and Energy Balance in Relation to Obesity and Co-morbidities

Dietary protein is effective for body-weight management, in that it promotes satiety, energy expenditure, and changes body-composition in favor of fat-free body mass. With respect to body-weight management, the effects of diets varying in protein differ according to energy balance. During energy restriction, sustaining protein intake at the level of requirement appears to be sufficient to aid body weight loss and fat loss. An additional increase of protein intake does not induce a larger loss of body weight, but can be effective to maintain a larger amount of fat-free mass. Protein induced satiety is likely a combined expression with direct and indirect effects of elevated plasma amino acid and anorexigenic hormone concentrations, increased diet-induced thermogenesis, and ketogenic state, all feed-back on the central nervous system. The decline in energy expenditure and sleeping metabolic rate as a result of body weight loss is less on a high-protein than on a medium-protein diet. In addition, higher rates of energy expenditure have been observed as acute responses to energy-balanced high-protein diets. In energy balance, high protein diets may be beneficial to prevent the development of a positive energy balance, whereas low-protein diets may facilitate this. High protein-low carbohydrate diets may be favorable for the control of intrahepatic triglyceride IHTG in healthy humans, likely as a result of combined effects involving changes in protein and carbohydrate intake. Body weight loss and subsequent weight maintenance usually shows favorable effects in relation to insulin sensitivity, although some risks may be present. Promotion of insulin sensitivity beyond its effect on body-weight loss and subsequent body-weight maintenance seems unlikely. In conclusion, higher-protein diets may reduce overweight and obesity, yet whether high-protein diets, beyond their effect on body-weight management, contribute to prevention of increases in non-alcoholic fatty liver disease NAFLD, type 2 diabetes and cardiovascular diseases is inconclusive.

A systematic review and narrative synthesis of interventions for uncomplicated obesity: weight loss, well-being and impact on eating disorders

OBJECTIVE

Most weight loss research focuses on weight as the primary outcome, often to the exclusion of other physiological or psychological measures. This study aims to provide a holistic evaluation of the effects from weight loss interventions for individuals with obesity by examining the physiological, psychological and eating disorders outcomes from these interventions.

METHODS

Databases Medline, PsycInfo and Cochrane Library (2011-2016) were searched for randomised controlled trials and systematic reviews of obesity treatments (dietary, exercise, behavioural, psychological, pharmacological or surgical). Data extracted included study features, risk of bias, study outcomes, and an assessment of treatment impacts on physical, psychological or eating disorder outcomes.

RESULTS

From 3628 novel records, 134 studies met all inclusion criteria and were evaluated in this review. Lifestyle interventions had the strongest evidence base as a first-line approach, with escalation to pharmacotherapy and bariatric surgery in more severe or complicated cases. Quality of life was the most common psychological outcome measure, and improved in all cases where it was assessed, across all intervention types. Behavioural, psychological and lifestyle interventions for weight loss led to improvements in cognitive restraint, control over eating and binge eating, while bariatric surgery led to improvements in eating behaviour and body image that were not sustained over the long-term.

DISCUSSION

Numerous treatment strategies have been trialled to assist people to lose weight and many of these are effective over the short-term. Quality of life, and to a lesser degree depression, anxiety and psychosocial function, often improve alongside weight loss. Weight loss is also associated with improvements in eating disorder psychopathology and related measures, although overall, eating disorder outcomes are rarely assessed. Further research and between-sector collaboration is required to address the significant overlap in risk factors, diagnoses and treatment outcomes between obesity and eating disorders.

The Health Consequences of Obesity in Young Adulthood

Young adults are gaining weight faster than any age group. This weight gain and the appearance of obesity-related comorbidities often commence in adolescence. Psychosocial distress and mental health issues are common and debilitating, and treatment approaches are likely to be similar to those for adolescents. At the same time, young adults may have physical morbidities which will continue and worsen throughout adulthood, such as hypertension, diabetes and polycystic ovarian syndrome. Health consequences of obesity are challenging to manage in young adults as their symptoms may be minimal, they are less likely to engage with healthcare due to other life priorities and their neurocognitive developmental stage makes therapy adherence difficult. Clinicians who manage young adults with obesity need to be aware of these age-specific challenges, as well as the sexual and reproductive health concerns that are present in this age group.

Protein intake and lean body mass preservation during energy intake restriction in overweight older adults

BACKGROUND

Dietary-induced weight loss is generally accompanied by a decline in skeletal muscle mass. The loss of muscle mass leads to a decline in muscle strength and impairs physical performance. A high dietary protein intake has been suggested to allow muscle mass preservation during energy intake restriction.

OBJECTIVE

To investigate the impact of increasing dietary protein intake on lean body mass, strength and physical performance during 12 weeks of energy intake restriction in overweight older adults.

DESIGN

Sixty-one overweight and obese men and women (63±5 years) were randomly assigned to either a high protein diet (HP; 1.7 g kg(-1) per day; n=31) or normal protein diet (NP; 0.9 g kg(-1) per day; n=30) during a 12-week 25% energy intake restriction. During this controlled dietary intervention, 90% of the diet was provided by the university. At baseline and after the intervention, body weight, lean body mass (dual-energy X-ray absorptiometry), leg strength (1-repetition maximum), physical performance (Short Physical Performance Battery, 400 m) and habitual physical activity (actigraph) were assessed.

RESULTS

Body weight declined in both groups with no differences between the HP and NP groups (-8.9±2.9 versus -9.1±3.4 kg, respectively; P=0.584). Lean body mass declined by 1.8±2.2 and 2.1±1.4 kg, respectively, with no significant differences between groups (P=0.213). Leg strength had decreased during the intervention by 8.8±14.0 and 8.9±12.8 kg, with no differences between groups (P=0.689). Physical performance as measured by 400 m walking speed improved in both groups, with no differences between groups (P=0.219).

CONCLUSIONS

Increasing protein intake above habitual intake levels (0.9 g kg(-1) per day) does not preserve lean body mass, strength or physical performance during prolonged energy intake restriction in overweight older adults.

Influence of dietary macronutrient composition on eating behaviour and self-perception in young women undergoing weight management

The control of eating behaviours such as hunger and disinhibition is problematic for women during weight management. Higher-protein (HP) diets have been shown to promote greater weight reduction than higher-carbohydrate (HC) diets, but their impact on eating behaviours is relatively unexplored. This study compared two iso-energetically restricted (5,600 kJ/day) diets differing in protein (HP: 32%, HC: 20%) and carbohydrate (HP: 41%, HC: 58%) on appetite ratings, restraint, disinhibition, perceived hunger and binge eating in 36 (HP: n = 21, HC: n = 15) young (18-25 years), healthy women with BMI ≥27.5 kg/m(2) who completed a 12-month clinical weight management trial. Dietary compliance and self-worth were also assessed. Results showed that both diets induced improvements in restraint and disinhibition from baseline (p < 0.01), with HP participants losing a non-significantly greater amount of weight than HC participants (HP: 9.6 ± 2.6, HC: 4.1 ± 1.4 kg, p = 0.07). Despite reasonable compliance, no significant appetite and eating behaviour differences were observed between the diets. Reduction in disinhibition (regardless of diet) significantly predicted weight loss (β = 0.574, p < 0.001) and self-worth improvement (β = -0.463, p = 0.002), while HP intake predicted greater self-worth change (β = -0.371, p = 0.011). This study demonstrates that young women can improve restraint and disinhibition on a weight management programme, with the reduction in disinhibition shown to be a key predictor of weight loss. HP intake may offer some advantage for increasing self-worth but not eating behaviours. As HP diets are popular, these findings warrant confirmation in a larger sample.

Long term weight maintenance after advice to consume low carbohydrate, higher protein diets--a systematic review and meta analysis

BACKGROUND

Meta analysis of short term trials indicates that a higher protein, lower carbohydrate weight loss diet enhances fat mass loss and limits lean mass loss compared with a normal protein weight loss diet. Whether this benefit persists long term is not clear.

METHODS AND RESULTS

We selected weight loss studies in adults with at least a 12 month follow up in which a higher percentage protein/lower carbohydrate diet was either planned or would be expected for either weight loss or weight maintenance. Studies were selected regardless of the success of the advice but difference in absolute and percentage protein intake at 12 months was used as a moderator in the analysis. Data was analysed using Comprehensive Meta analysis V2 using a random effects analysis. As many as 32 studies with 3492 individuals were analysed with data on fat and lean mass, glucose and insulin from 18 to 22 studies and lipids from 28 studies. A recommendation to consume a lower carbohydrate, higher protein diet in mostly short term intensive interventions with long term follow up was associated with better weight and fat loss but the effect size was small-standardised means of 0.14 and 0.22, p = 0.008 and p < 0.001 respectively (equivalent to 0.4 kg for both). A difference of 5% or greater in percentage protein between diets at 12 mo was associated with a 3 fold greater effect size compared with <5% (p = 0.038) in fat mass (0.9 vs. 0.3 kg). Fasting triglyceride and insulin were also lower with high protein diets with effect sizes of 0.17 and 0.22, p = 0.003 and p = 0.042 respectively. Other lipids and glucose were not different.

CONCLUSION

The short term benefit of higher protein diets appears to persist to a small degree long term. Benefits are greater with better compliance to the diet.

Iron, hepcidin and inflammatory status of young healthy overweight and obese women in Australia

BACKGROUND AND AIMS

Evidence suggests obesity-related inflammation alters iron metabolism potentially increasing the risk of iron deficiency. This cross-sectional study aimed to investigate iron, hepcidin and inflammatory status in young, healthy overweight and obese women.

METHODS

114 young (18-25 years), healthy comorbidity-free women with a body mass index (BMI) ≥27.5 kg/m(2) were recruited. Biochemical data were analysed using mean ± standard deviation or median (interquartile range) and multivariate modelling. Biochemical markers were also stratified according to varying degrees of overweight and obesity.

RESULTS

Anaemia (haemoglobin <120 g/l) and iron deficiency (serum ferritin <15.0 µg/l) were prevalent in 10% and 17% of participants respectively. Mean/median soluble transferrin receptor was 1.61±0.44 mg/l; hepcidin 6.40 (7.85) ng/ml and C-reactive protein (CRP) 3.58 (5.81) mg/l. Multivariate modelling showed that BMI was a significant predictor of serum iron (coefficient = -0.379; standard error = 0.139; p = 0.008), transferrin saturation (coefficient = -0.588; standard error = 0.222; p = 0.009) and CRP (coefficient = 0.127; standard error = 0.024; p<0.001). Stratification of participants according to BMI showed those with ≥35.0 kg/m(2) had significantly higher CRP (p<0.001) than those in lower BMI categories.

CONCLUSIONS

Increasing obesity was associated with minor disturbances in iron metabolism. However, overall outcomes indicated simple iron deficiency (hypoferritinaemia) was the primary iron-related abnormality with no apparent contribution of inflammation or hepcidin, even in those with BMI >35.0 kg/m(2). This indicates that obesity alone may not be sufficient to induce clinically significant disturbances to iron metabolism as previously described. This may be attributed to the lack of comorbidity in this cohort.