Some problems with Cochrane reviews of diet and chronic disease High-protein, low-fat diets are effective for weight loss and favorably alter biomarkers in healthy adults. A randomized trial of energy-restricted high-protein versus high-carbohydrate, low-fat diet in morbid obesity. A randomized controlled trial of the effect on blood pressure of dietary non-meat protein versus meat protein in normotensive omnivores. Effect of a high-protein diet on kidney function in healthy adults: results from the OmniHeart trial. Long-term effects of advice to consume a high-protein, low-fat diet, rather than a conventional weight-loss diet, in obese adults with Type 2 diabetes: one-year follow-up of a randomised trial Does a high-protein diet improve weight loss in overweight and obese children? Route, early or energy? … Protein improves protein balance in critically ill patients The effect of high-protein, low-carbohydrate diets in the treatment of type 2 diabetes: a 12 month randomised controlled trial Animal Protein, Animal Fat, and Cholesterol Intakes and Risk of Cerebral Infarction Mortality in the Adult Health Study The effects of a high protein diet on indices of health and body composition – a crossover trial in resistance-trained men Effects of dietary protein intake on indexes of hydration. Effects of Weight Loss and Long-Term Weight Maintenance With Diets Varying in Protein and Glycemic Index on Cardiovascular Risk Factors: The Diet, Obesity, and Genes (DiOGenes) Study A Randomized, Controlled Trial RCT of a high-protein diet on hunger motivation and weight-loss in obese children: an extension and replication. Comparison of 2 weight-loss diets of different protein content on bone health: a randomized trial. CONTROLLED STUDY OF THE EFFECTS OF DIETARY PROTEIN ON BLOOD PRESSURE IN NORMOTENSIVE HUMANS Effects of high‐protein diets on fat‐free mass and muscle protein synthesis following weight loss: a randomized controlled trial
The sum of evidence -based nutrition has to be more than a Cochrane-type meta- analysis of r and omised controlled trials ( RCTs ) . Most of the evidence base in nutrition is observational , especially cohort studies . RCTs of diet change through to disease outcome are uncommon and the change has usually been addition or removal of only a single food component . Trials with whole diets through to disease outcome are rare and dietary changes made by individuals are unlikely to be an exact copy of the prescription . It is hard to even imagine a trial in which half ( r and omised ) of a large group of middle-aged people agree to avoid vegetables for 5 y and be followed up to see who will develop cancer . Most of the USA 's health cl aims , permitted by the Food and Drug Administration , are not supported by RCTs . But where controlled trials of nutritional change and disease outcome have been achieved , they must be review ed very carefully . Two Cochrane review s on diet and cardiovascular disease ( CVD ) , published in the widely read British Medical Journal ( BMJ ) , were criticised after their publication and the conclusions have not been subsequently adopted by expert committees . The first of these review s was ‘ Dietary fat and prevention of CVD : a systematic review ’ . The second was ‘ Systematic review of long term effects of advice to reduce dietary salt in adults ’ . A critique of these two Cochrane review s is presented here as a contribution to our discussion of the potential of Cochrane methodology to the reliability of knowledge about diet and disease Although popular and effective for weight loss , low-carbohydrate , high-protein , high-fat ( Atkins ) diets have been associated with adverse changes in blood and renal biomarkers . High-protein diets low in fat may represent an equally appealing diet plan but promote a more healthful weight loss .  Healthy adults ( n = 20 ) were r and omly assigned to 1 of 2 low-fat ( < 30 % energy ) , energy-restricted groups : high-protein ( 30 % energy ) or high-carbohydrate ( 60 % energy ) ; 24-h intakes were strictly controlled during the 6-wk trial . One subject from each group did not complete the trial due to out-of-state travel ; two subjects in the high-carbohydrate group withdrew from the trial due to extreme hunger . Body composition and metabolic indices were assessed pre- and post-trial . Both diets were equally effective at reducing body weight ( -6 % , P < 0.05 ) and fat mass ( -9 to -11 % , P < 0.05 ) ; however , subjects consuming the high-protein diet reported more satisfaction and less hunger in mo 1 of the trial . Both diets significantly lowered total cholesterol ( -10 to -12 % ) , insulin ( -25 % ) , and uric acid ( -22 to -30 % ) concentrations in blood from fasting subjects . Urinary calcium excretion increased 42 % in subjects consuming the high-protein diet , mirroring the 50 % increase in dietary calcium with consumption of this diet ; thus , apparent calcium balance was not adversely affected . Creatinine clearance was not altered by diet treatments , and nitrogen balance was more positive in subjects consuming the high-protein diet vs. the high-carbohydrate diet ( 3.9 + /- 1.4 and 0.7 + /- 1.7 g N/d , respectively , P < 0.05 ) . Thus , low-fat , energy-restricted diets of varying protein content ( 15 or 30 % energy ) promoted healthful weight loss , but diet satisfaction was greater in those consuming the high-protein diet OBJECTIVE Conflicting evidence exists as to weight loss produced by diets with different carbohydrate/protein ratio . The aim was to compare the long-term effects of high-protein vs. high-carbohydrate diet ( HPD , HCD ) , combined with cognitive behavior therapy ( CBT ) . DESIGN AND METHODS In a r and omized trial , 88 obese participants ( mean age , 46.7 ; mean BMI , 45.6 kg m(-2 ) ) were enrolled in a 3-week inpatient and 48-week outpatient treatment , with continuous CBT during the study period . All subjects consumed a restricted diet ( 1,200 kcal day(-1 ) for women , 1,500 for men ; 20 % energy from fat , < 10 % saturated fat ) . HPD derived 34 % energy from proteins , 46 % from carbohydrates ; HCD 17 % from proteins , 64 % from carbohydrates . The primary outcome was 1-year percent weight loss . Secondary outcomes were attrition rates and changes in cardiovascular risk factors and psychological profile . RESULTS Attrition rates were similar between groups ( 25.6 % ) . In the intention-to-treat analysis , weight loss averaged 15.0 % in HPD and 13.3 % in HCD at 1 year , without any difference throughout the study period . Both diets produced a similar improvement in secondary outcomes . CONCLUSIONS The relative carbohydrate and protein content of the diet , when combined with intensive CBT , does not significantly affect attrition rate , weight loss and psychosocial outcome in patients with severe obesity 1 . A r and omized , controlled trial was carried out to examine whether changes in type and amount of dietary protein were responsible for earlier observations of blood-pressure-lowering effects of lacto-ovo-vegetarian diets . 2 . Sixty-four subjects were pair-matched for sex , age , weight and sitting systolic blood pressure , and were r and omly allocated to receive one of two types of protein supplement : one containing proteins from meat , the other proteins from non-meat sources . The supplements were balanced in terms of other nutrients . Consumption of other meat , poultry or fish was prohibited . 3 . Sitting and st and ing blood pressures , weight , dietary intakes and plasma and urinary electrolytes were measured at regular intervals during the 12 weeks of trial . Urinary 3-methylhistidine was used as a measure of compliance . 4 . Fifty subjects completed the trial . There were no statistically significant blood pressure differences between groups either at baseline or at end-of-trial , neither were there any substantive differences in mean blood pressure changes between baseline and end-of-trial . 3-Methyl-histidine excretion was significantly lower in subjects on the non-meat diet . 5 . The results suggest that the protein components of the lacto-ovo-vegetarian diet are not responsible for the blood-pressure-lowering effects of that diet BACKGROUND Consumption of a diet high in protein can cause glomerular hyperfiltration , a potentially maladaptive response , which may accelerate the progression of kidney disease . STUDY DESIGN An ancillary study of the OmniHeart trial , a r and omized 3-period crossover feeding trial testing the effects of partial replacement of carbohydrate with protein on kidney function . SETTING & PARTICIPANTS Healthy adults ( N=164 ) with prehypertension or stage 1 hypertension at a community-based research clinic with a metabolic kitchen . INTERVENTION Participants were fed each of 3 diets for 6 weeks . Feeding periods were separated by a 2- to 4-week washout period . Weight was held constant on each diet . The 3 diets emphasized carbohydrate , protein , or unsaturated fat ; dietary protein was either 15 % ( carbohydrate and unsaturated fat diets ) or 25 % ( protein diet ) of energy intake . OUTCOMES Fasting serum creatinine , cystatin C , and β2-microglobulin levels , estimated glomerular filtration rate ( eGFR ) . MEASUREMENTS Serum creatinine , cystatin C , and β2-microglobulin collected at the end of each feeding period . RESULTS Baseline cystatin C-based eGFR was 92.0±16.3 ( SD ) mL/min/1.73 m(2 ) . Compared with the carbohydrate and unsaturated fat diets , the protein diet increased cystatin C-based eGFR by ~4 mL/min/1.73 m(2 ) ( P < 0.001 ) . The effects of the protein diet on kidney function were independent of changes in blood pressure . There was no significant difference between the carbohydrate and unsaturated fat diets . LIMITATIONS Participants did not have kidney disease at baseline . CONCLUSIONS A healthy diet rich in protein increased eGFR . Whether long-term consumption of a high-protein diet leads to kidney disease is uncertain Aims /hypothesisThis study compared the long-term weight loss and health outcomes at 1-year follow-up , after a 12-week intensive intervention consisting of two low-fat , weight-loss diets , which differed in protein content . Methods We r and omly assigned 66 obese patients ( BMI : 27–40 kg/m2 ) with Type 2 diabetes to either a low-protein ( 15 % protein , 55 % carbohydrate ) or high-protein diet ( 30 % protein , 40 % carbohydrate ) for 8 weeks of energy restriction ( ~6.7 MJ/day ) and 4 weeks of energy balance . Subjects were asked to maintain the same dietary pattern for a further 12 months of follow-up . Results The study was completed by 38 of the subjects , with equal dropouts in each group . At Week 64 , weight reductions against baseline were −2.2±1.1 kg ( low protein ) and −3.7±1.0 kg ( high protein ) , p<0.01 , with no diet effect . Fat mass was not different from baseline in either group . At Week 12 , both diets reduced systolic and diastolic blood pressure by 6 and 3 mm Hg respectively , but blood pressure increased more with weight regain during follow-up in the low-protein group ( p≤0.04 ) . At Week 64 , both diets significantly increased HDL cholesterol and lowered C-reactive protein concentrations . There was no difference in the urinary urea : creatinine ratio at baseline between the two groups , but this ratio increased at Week 12 ( in the high-protein group only , p<0.001 , diet effect ) , remaining stable during follow-up in both diets . Conclusions /interpretationA high-protein weight-reduction diet may in the long term have a more favourable cardiovascular risk profile than a low-protein diet with similar weight reduction in people with Type 2 diabetes OBJECTIVE To evaluate the effect of a high-protein diet on anthropometry , body composition , subjective appetite , and mood sensations in overweight and obese children attending a residential weight-loss camp . RESEARCH METHODS AND PROCEDURES Children ( 120 ; BMI , 33.1 + /- 5.5 kg/m(2 ) ; age , 14.2 + /- 1.9 years ) were r and omly assigned to either a st and ard or high-protein diet group ( 15 % vs. 22.5 % protein , respectively ) . All children were assessed at baseline and at the end of the camp for anthropometry , body composition , blood pressure , biochemical variables ( n = 27 ) , and subjective appetite and mood sensations ( n = 50 ) . RESULTS Attendance at the weight-loss camp result ed in significant improvements in most measures . Campers lost 5.5 + /- 2.9 kg in body weight ( p < 0.001 ) and 3.8 + /- 5.4 kg in fat mass ( p < 0.001 ) and reduced their BMI st and ard deviation score by 0.27 + /- 0.1 ( p < 0.001 ) and their waist circumference by 6.6 + /- 2.8 cm ( p < 0.001 ) . Subjective sensations of hunger increased significantly over the camp duration , but no other changes in appetite or mood were observed . There were no significant differences between the two diets on any physical or subjective measures . DISCUSSION Weight-loss camps are effective in assisting children to lose weight and improve on a range of health outcomes , independently of the protein content of the diet . The implication s of an increase in hunger associated with weight loss needs to be considered . Further work is warranted to investigate whether higher levels of dietary protein are feasible or effective in longer-term weight-loss interventions of this type The critical care community still has mixed feelings when considering the optimal nutrition of intensive care unit ( ICU ) patients , which is underst and able as r and omized controlled trials have not been very helpful in improving clinical practice . There have been no r and omized controlled trials ( RCTs ) to contribute to the discussion , especially concerning the role of enterally fed protein in optimal critical care . Recent studies on the route of feeding have shown that enteral nutrition ( EN ) is not necessarily superior to parenteral nutrition ( PN ) [ 1 , 2 ] . There appears to be a strong consensus , with backup from a meta- analysis , on the preferential use of EN over PN [ 3 ] . The infection rate was especially used as an argument ; however , this is not substantiated in recent trials [ 1 , 2 ] . We have to consider how applicable this current knowledge is to all ICU patients . Early EN is still the preferred way of feeding [ 3 ] . Starting feeding early may improve the outcome of ICU patients . RCTs have all investigated ( supplemental parenteral )  energy delivery [ 4 ] . Only two trials have ‘ considered ’ protein : the PERMIT trial [ 5 ] ( protein supplemented , equal level ) and EAT-ICU trial [ 6 ] ( protein supplemented , higher level ) . Early energy delivery should be applied cautiously since it appears to be related to worse outcome in ICU patients [ 7 , 8 , 9 ] . Therefore , and from the perspective of clinical practice , the Swiss Supplemental PN ( SPN ) trial appears to provide the most logical design [10]—start with early EN and evaluate on day 3 what the level of energy delivery is ; when delivery levels are low ( < 60 % ) start supplementation PN . In clinical practice in our ICU the enteral feeding levels are high enough to avoid PN supplementation , which therefore restricts the specific indication to use PN . The focus of this research has been caloric delivery . There are more than enough observational data to support that higher protein delivery is associated with improved outcome in ICU patients [ 7 , 8 , 9 ] . These observational studies clearly show the benefit of higher protein delivery . However , they are considered relatively weak evidence since illness is considered a confounding factor in the relationship between delivery and outcome for which we can not completely adjust . R and omized trials have not been conducted , although two trials with r and omized high(er ) amino acid infusion are available and somewhat contradicting [ 11 , 12 ] . As with the studies on caloric delivery , the studies on protein have been hampered by insufficient knowledge on energy and protein metabolism under these (patho)physiological circumstances in the ICU patient [ 7 , 8 , 9 ] . Therefore , mechanistic studies on the protein physiology in ICU patients is an essential and current development . The Swedish group of Wernerman and Rooyackers has provided crucial information on the topic . They showed that it was possible to change protein balance during the early phase of admission to the ICU from negative to positive by a short-term ( 3-h ) high-level ( 1 g/kg/day ) amino acid ( AA ) infusion [ 13 ] . This observation was very important to help underst and the physiology since it showed that , under these circumstances of critical illness , some basic principles of nutrition still perform well . In the December 2017 issue of Critical Care , Sundstrom et al. showed that the effect of supplemental AA infusion at 3 h is still present at 24 h [ 14 ] . Why is this so important to know ? We know from extensive studies in sports and the elderly that protein synthesis can be stimulated by bolus protein feeding ; however , we know relatively little about the effects of continuous ( low dose per time unit ) feeding . While the absolute levels of protein balance still have to be considered with caution ( e.g. , choice of tracer ) , and we are not completely sure where the protein is going , we now know this positive effect on protein balance is lasting . The next challenge is to reconnect this physiological information with the outcome of ICU patients . We have shown that muscle ( protein ) mass at admission to the ICU is relevant for the outcome of ICU patients [ 15 ] . We do not know if we can change muscle mass and outcome of ICU patients with protein nutrition . The study by Sundstrom et al. [ 14 ] is very promising for protein balance , but will that be enough to change outcome ? And , if so , is that true for all patients —does one size fit all ? The ICU patient group is heterogeneous . Earlier , we found high protein delivery to be associated with lower mortality , except for sepsis patients and patients with early caloric overfeeding [ 7 ] . The EAT-ICU trial did not find an effect of early goal -directed feeding on physical component score at 6 months or on mortality [ 6 ] . Goal -directed feeding included feeding energy based on indirect calorimetry and protein up to 1.5 g/kg/day from day 1 . Feeding calories up to the measured caloric target from day 1 may be equal to caloric overfeeding [ 7 ] . The 47 % of patients with sepsis in the EAT-ICU trial might also not benefit from the higher protein feeding [ 7 ] . Therefore , the effects of protein and energy can not be assessed individually from this trial . Ferrie et al. showed interesting differences in muscle mass and function between an AA infusion rate of 0.8 and 1.2 g/kg/day [ 12 ] , but not all patients are equal — one size does not fit all ! Those patients with a low protein reserve ( low muscle mass ) may be at highest risk in the ICU and may benefit more from intervention with early protein nutrition . We have to await further studies , including r and omized studies and post-hoc observational studies , to further develop this area of interest . The studies trying to underst and the mechanism behind the physiological effect are important as well ; we might come nearer to the truth of what works and what does not work in ICU nutrition Aims /hypothesisShort-term dietary studies suggest that high-protein diets can enhance weight loss and improve glycaemic control in people with type 2 diabetes . However , the long-term effects of such diets are unknown . The aim of this study was to determine whether high-protein diets are superior to high-carbohydrate diets for improving glycaemic control in individuals with type 2 diabetes . Methods Overweight/obese individuals ( BMI 27–40 kg/m2 ) with type 2 diabetes ( HbA1c 6.5–10 % ) were recruited for a 12 month , parallel design , dietary intervention trial conducted at a diabetes specialist clinic ( Melbourne , VIC , Australia ) . Of the 108 initially r and omised , 99 received advice  to follow low-fat ( 30 % total energy ) diets that were either high in protein ( 30 % total energy , n = 53 ) or high in carbohydrate ( 55 % total energy , n = 46 ) . Dietary assignment was done by a third party using computer-generated r and om numbers . The primary endpoint was change in HbA1c . Secondary endpoints included changes in weight , lipids , blood pressure , renal function and calcium loss . Study endpoints were assessed blinded to the diet group , but the statistical analysis was performed unblinded . This study used an intention-to-treat model for all participants who received dietary advice . Follow-up visits were encouraged regardless of dietary adherence and last measurements were carried forward for study non-completers . Results Ninety-nine individuals were included in the analysis ( 53 in high protein group , 46 in high carbohydrate group ) . HbA1c decreased in both groups over time , with no significant difference between groups ( mean difference of the change at 12 months ; 0.04 [ 95 % CI −0.37 , 0.46 ] ; p = 0.44 ) . Both groups also demonstrated decreases over time in weight , serum triacylglycerol and total cholesterol , and increases in HDL-cholesterol . No differences in blood pressure , renal function or calcium loss were seen . Conclusions /interpretationThese results suggest that there is no superior long-term metabolic benefit of a high-protein diet over a high-carbohydrate in the management of type 2 diabetes . Trial registration ACTRN12605000063617 ( www.anzctr.org.au ) . Funding This study was funded by a nutritional research grant from Meat and Livestock Australia ( MLA ) . J.E. Shaw is supported by NHMRC Fellowship 586623 Background and Purpose — A traditional diet that is poor in animal products is thought to explain the high rate of stroke in Asian population s. The purpose of the present study was to examine the effect of a diet rich in animal protein , animal fat , and cholesterol on the risk of  cerebral infa rct ion mortality in a Japanese population . Methods — A prospect i ve study of 3731 Japanese men and women aged 35 to 89 years was conducted from 1984 to 2001 . Nutrient intake was estimated at baseline from the responses to a 24-hour diary . During the follow-up period , cases of cerebral infa rct ion deaths ( as entered on death certificates ) were monitored . Results — During the follow-up period , 60 deaths were attributed to cerebral infa rct ion . A high intake of animal fat and cholesterol was significantly associated with a reduced risk of cerebral infa rct ion death . The risk was reduced by 62 % ( CI , 82 % to 18 % ) for those in the third tertile of animal fat intake , compared with those in the first tertile , with a significant linear dose-response relationship ( P = 0.0073 ) . The risk of death from infa rct ion was reduced by 63 % ( CI , 82 % to 22 % ) in the high cholesterol consumption group , compared with the low consumption group . A significant linear dose – response relationship was observed . Animal protein was not significantly associated with infa rct ion mortality after adjustment for animal fat and cholesterol . Conclusions — This study suggests that in Japan , where animal product intake is lower than in Western countries , a high consumption of animal fat and cholesterol was associated with a reduced risk of cerebral infa rct ion death Background Eight weeks of a high protein diet ( > 3 g/kg/day ) coupled with a periodized heavy resistance training program has been shown to positively affect body composition with no deleterious effects on health . Using a r and omized , crossover design , resistance-trained male subjects underwent a 16-week intervention ( i.e. , two 8-week periods ) in which they consumed either their normal ( i.e. , habitual ) or a higher protein diet ( > 3 g/kg/day ) . Thus , the purpose of this study was to ascertain if significantly increasing protein intake would affect clinical markers of health ( i.e. , lipids , kidney function , etc . ) as well as performance and body composition in young males with extensive resistance training experience . Methods Twelve healthy resistance-trained men volunteered for this study ( mean ± SD : age 25.9 ± 3.7 years ; height 178.0 ± 8.5 cm ; years of resistance training experience 7.6 ± 3.6 ) with 11 subjects completing most of the assessment s. In a r and omized crossover trial , subjects were tested at baseline and after two 8-week treatment periods ( i.e. , habitual [ normal ] diet and high protein diet ) for body composition , measures of health ( i.e. , blood lipids , comprehensive metabolic panel ) and performance . Each subject maintained a food diary for the 16-week treatment period ( i.e. , 8 weeks on their normal or habitual diet and 8 weeks on a high protein diet ) . Each subject provided a food diary of two weekdays and one weekend day per week . In addition , subjects kept a diary of their training regimen that was used to calculate total work performed . Results During the normal and high protein phase of the treatment period , subjects consumed 2.6 ± 0.8 and 3.3 ± 0.8 g/kg/day of dietary protein , respectively . The mean protein intake over the 4-month period was 2.9 ± 0.9 g/kg/day . The high protein group consumed significantly more calories and protein ( p < 0.05 ) than the normal protein group . There were no differences in dietary intake between the groups for any other measure . Moreover , there were no significant changes in body composition or markers of health in either group . There were no side effects ( i.e. , blood lipids , glucose , renal , kidney function etc . ) regarding high protein consumption . Conclusion In resistance-trained young men who do not significantly alter their training regimen , consuming a high protein diet ( 2.6 to 3.3 g/kg/day ) over a 4-month period has no effect on blood lipids or markers of renal and hepatic function . Nor were there any changes in performance or body composition . This is the first crossover trial using resistance-trained subjects in which the elevation of protein intake to over four times the recommended dietary allowance has shown no harmful effects This study aims to characterize the relationship between increased protein intake and hydration indexes . Five men participated in a 12-week , r and omized , crossover , controlled diet intervention study . Subjects consumed eucaloric diets containing 3.6 ( high protein ) , 1.8 ( moderate protein ) , and 0.8 ( low protein ) g/kg/day of protein for 4 weeks each . Energy intakes were based on requirements established relative to resting energy expenditure and activity at baseline . Assessment s included blood urea nitrogen , plasma osmolality , urine-specific gravity , and estimates of fluid balance . Repeated- measures analyses of variance and paired t tests were used to determine effects of treatment and time . Fluid intake and fluid balance were unaffected . Blood urea nitrogen was higher for high protein vs low protein and vs moderate protein , and urine-specific gravity was higher for high protein vs moderate protein . Baseline plasma osmolality was greater for high protein vs low protein and vs moderate protein . The effect of increasing dietary protein on fluid status was minimal Background — We sought to separately examine the effects of either weight loss or diets varying in protein content and glycemic index without further changes in body weight on cardiovascular risk factors within the Diet , Obesity , and Genes study ( DiOGenes ) . Methods and Results — DiOGenes is a pan-European controlled dietary intervention study in 932 overweight adults who first lost body weight on an 8-week low-calorie diet and were then r and omized to 1 of 5 ad libitum diets for 26 weeks .  The diets were either high or low protein or high or low glycemic index in 4 combinations or control . Weight loss ( −11.23 kg ; 95 % confidence interval , −11.54 to −10.92 ; P<0.001 ) reduced high-sensitivity C-reactive protein ( −1.15 mg/L ; 95 % confidence interval , −1.30 to −0.41 ; P<0.001 ) , low- and high-density lipoprotein cholesterol , triglycerides , and blood pressure . During the 26-week weight maintenance period in the intention-to-treat analysis , the further decrease of high-sensitivity C-reactive protein blood levels was −0.46 mg/L greater ( 95 % confidence interval , −0.79 to −0.13 ) in the groups assigned to low-glycemic-index diets than in those on high-glycemic-index diets ( P<0.001 ) . Groups on low-protein diets achieved a −0.25 mg/L greater reduction in high-sensitivity C-reactive protein ( 95 % confidence interval , −0.59 to −0.17 ) than those on high-protein diets ( P<0.001 ) , whereas lipid profiles and blood pressure were not differently affected . Conclusions — This large-scale intervention study clearly separates weight loss from dietary composition – related effects . Low-glycemic-index carbohydrates and , to a lesser extent , low-protein intake may specifically reduce low- grade inflammation and associated comorbidities in overweight/obese adults . Clinical Trial Registration — http://www . clinical trials.gov . Unique identifier : NCT00390637 This study aim ed to evaluate the weight loss and hunger motivation effects of an energy-restricted high-protein ( HP ) diet in overweight and obese children . In total , 95 overweight and obese children attended an 8-week ( maximum ) program of physical activity , reduced-energy intake , and behavior change education . Children were r and omly assigned to one of two isoenergetic diets ( st and ard ( SP ) : 15 % protein ; HP : 25 % protein ) , based on individually estimated energy requirements . Anthropometry and body composition were assessed at the start and end of the program and appetite and mood ratings completed on the first 3 consecutive weekdays of each week children attended camp . The HP diet had no greater effect on weight loss , body composition , or changes in appetite or mood when compared to the SP diet . Overall , campers lost 5.2 + /- 3.0 kg in body weight and reduced their BMI st and ard deviation score ( sds ) by 0.25 . Ratings of desire to eat increased significantly over the duration of the intervention , irrespective of diet . This is the third time we have reported an increase in hunger motivation in weight-loss campers and replicates our previous failure to block this with a higher protein diet . Further work is warranted into the management of hunger motivation as a result of negative energy balance BACKGROUND It has been hypothesized that hip-fracture rates are higher in developed than in developing countries because high-protein ( HP ) Western diets induce metabolic acidosis and hypercalciuria . Confounders include interactions between dietary protein and calcium , sodium , and potassium . OBJECTIVE We determined whether an HP or a high-normal-protein ( HNP ) weight-loss diet caused greater loss in bone mineral density ( BMD ) over 24 mo . DESIGN The Weight Loss , Protein and Bone Density Study was conducted from 2008 to 2011 in 323 overweight [ body mass index ( BMI ; in kg/m(2 ) ) > 27 ] postmenopausal women , with a total hip BMD t score less than -2.0 . Subjects were r and omly assigned to receive an isocaloric calcium-replete HP ( ≥90 g protein/d ) or HNP ( < 80 g protein/d ) weight-loss diet , with the aim of a difference of 20 g protein/d . A total of 186 subjects ( 90 subjects in the HP group , 96 subjects in the HNP group ) completed 12 mo , and 137 subjects ( 69 subjects in the HP group , 68 subjects in the HNP group ) completed 24 mo . RESULTS Biomarkers confirmed a difference in protein intake of 16 and 13.1 g at 12 and 24 mo , respectively . Mean ( ±SE ) weight loss was equal ; HP subjects lost 7.9 ± 0.9 kg and HNP subjects lost 8.9 ± 0.9 kg at 24 mo . Subjects lost 1 - 2 % BMD annually at lumbar spine vertebrae 2 - 4 , the forearm , the femoral neck , and hip . ANCOVA showed no effect of the HP or HNP diet ( P > 0.05 for diet and diet-time interactions ) . A diet-by-time analysis showed that the HNP diet increased C-terminal telopeptide and osteocalcin ( P ≤ 0.001 for each ) despite hypercalciuria ( P = 0.029 ) . CONCLUSION High dietary protein intake during weight loss has no clinical ly significant effect on bone density but slows bone turnover . This trial was registered at the Australian and New Zeal and Clinical Trials Registry ( http://www.anzctr.org.au ) as ACTRN12608000229370 1 . The object of this study was to determine whether meat protein per se is responsible for the higher blood pressures ( BP )  in omnivores compared with vegetarians The purpose of this work was to determine the effects of varying levels of dietary protein on body composition and muscle protein synthesis during energy deficit ( ED ) . A r and omized controlled trial of 39 adults assigned the subjects  diets providing protein at 0.8 ( recommended dietary allowance ; RDA ) , 1.6 ( 2X‐RDA ) , and 2.4 ( 3X‐RDA ) g kg–1 d–1 for 31 d. A 10‐d weight‐maintenance ( WM ) period was followed by a 21 d , 40 % ED . Body composition and postabsorptive and postpr and ial muscle protein synthesis were assessed during WM ( d 9‐10 ) and ED ( d 30‐31 ) . Volunteers lost ( P<0.05 ) 3.2 ± 0.2 kg body weight during ED regardless of dietary protein . The proportion of weight loss due to reductions in fat‐free mass was lower ( P<0.05 ) and the loss of fat mass was higher ( P<0.05 ) in those receiving 2X‐RDA and 3X‐RDA compared to RDA . The anabolic muscle response to a protein‐rich meal during ED was not different ( P>0.05 ) from WM for 2X‐RDA and 3X‐RDA , but was lower during ED than WM for those consuming RDA levels of protein ( energy × protein interaction , P<0.05 ) . To assess muscle protein metabolic responses to varied protein intakes during ED , RDA served as the study control . In summary , we determined that consuming dietary protein at levels exceeding the RDA may protect fat‐free mass during short‐term weight loss .— Pasiakos , S. M. , Cao , J. J. , Margolis , L. M. , Sauter , E. R. , Whigham , L. D. , McClung , J. P. , Rood , J. C. , Carbone , J. W. , Combs , G. F. , Jr. , Young , A. J. Effects of high‐protein diets on fat‐free mass and muscle protein synthesis following weight loss : a r and omized controlled trial . FASEB J. 27 , 3837–3847 ( 2013 ) .
Adverse gastrointestinal events were more common with high-protein diets .
Multivariable meta-regression analysis showed no significant dose response with higher protein intake .
Conclusions : Higher-protein diets  probably improve adiposity , blood pressure and triglyceride levels , but these effects are small and need to be weighed against the potential for harms
Background / Objectives : Numerous r and omised controlled trials ( RCTs ) published in first tier medical journals have evaluated the health effects of diets high in protein .
We conducted a rigorous systematic review of RCTs comparing higher- and lower-protein diets .