Lisa Te Morenga

Dietary sugars and body weight: systematic review and meta-analyses of randomised controlled trials and cohort studies.

Objective To summarise evidence on the association between intake of dietary sugars and body weight in adults and children. Design Systematic review and meta-analysis of randomised controlled trials and prospective cohort studies. Data sources OVID Medline, Embase, PubMed, Cumulative Index to Nursing and Allied Health Literature, Scopus, and Web of Science (up to December 2011). Review methods Eligible studies reported the intake of total sugars, intake of a component of total sugars, or intake of sugar containing foods or beverages; and at least one measure of body fatness. Minimum duration was two weeks for trials and one year for cohort studies. Trials of weight loss or confounded by additional medical or lifestyle interventions were excluded. Study selection, assessment, validity, data extraction, and analysis were undertaken as specified by the Cochrane Collaboration and the GRADE working group. For trials, we pooled data for weight change using inverse variance models with random effects. We pooled cohort study data where possible to estimate effect sizes, expressed as odds ratios for risk of obesity or β coefficients for change in adiposity per unit of intake. Results 30 of 7895 trials and 38 of 9445 cohort studies were eligible. In trials of adults with ad libitum diets (that is, with no strict control of food intake), reduced intake of dietary sugars was associated with a decrease in body weight (0.80 kg, 95% confidence interval 0.39 to 1.21; P<0.001); increased sugars intake was associated with a comparable weight increase (0.75 kg, 0.30 to 1.19; P=0.001). Isoenergetic exchange of dietary sugars with other carbohydrates showed no change in body weight (0.04 kg, −0.04 to 0.13). Trials in children, which involved recommendations to reduce intake of sugar sweetened foods and beverages, had low participant compliance to dietary advice; these trials showed no overall change in body weight. However, in relation to intakes of sugar sweetened beverages after one year follow-up in prospective studies, the odds ratio for being overweight or obese increased was 1.55 (1.32 to 1.82) among groups with the highest intake compared with those with the lowest intake. Despite significant heterogeneity in one meta-analysis and potential bias in some trials, sensitivity analyses showed that the trends were consistent and associations remained after these studies were excluded. Conclusions Among free living people involving ad libitum diets, intake of free sugars or sugar sweetened beverages is a determinant of body weight. The change in body fatness that occurs with modifying intakes seems to be mediated via changes in energy intakes, since isoenergetic exchange of sugars with other carbohydrates was not associated with weight change.

Dietary sugars and cardiometabolic risk: systematic review and meta-analyses of randomized controlled trials of the effects on blood pressure and lipids

BACKGROUND Dietary sugars have been suggested as a cause of obesity, several chronic diseases, and a range of cardiometabolic risk factors, but there is no convincing evidence of a causal relation between sugars and risk factors other than body weight. OBJECTIVE We conducted a systematic review and meta-analysis of randomized controlled trials that examined effects of the modification of dietary free sugars on blood pressure and lipids. DESIGN Systematic searches were conducted in OVID Medline, Embase, Scopus, Cumulative Index to Nursing and Allied Health Literature, and Web of Science databases (to August 2013) to identify studies that reported intakes of free sugars and at least one lipid or blood pressure outcome. The minimum trial duration was 2 wk. We pooled data by using inverse-variance methods with random-effects models. RESULTS A total of 39 of 11,517 trials identified were included; 37 trials reported lipid outcomes, and 12 trials reported blood pressure outcomes. Higher compared with lower sugar intakes significantly raised triglyceride concentrations [mean difference (MD): 0.11 mmol/L; 95% CI: 0.07, 0.15 mmol/L; P < 0.0001], total cholesterol (MD: 0.16 mmol/L; 95% CI: 0.10, 0.24 mmol/L; P < 0.0001), low-density lipoprotein cholesterol (0.12 mmol/L; 95% CI: 0.05, 0.19 mmol/L; P = 0.0001), and high-density lipoprotein cholesterol (MD: 0.02 mmol/L; 95% CI: 0.00, 0.03 mmol/L; P = 0.03). Subgroup analyses showed the most marked relation between sugar intakes and lipids in studies in which efforts were made to ensure an energy balance and when no difference in weight change was reported. Potential explanatory factors, including a weight change, in most instances explained <15% of the heterogeneity between studies (I(2) = 36-75%). The effect of sugar intake on blood pressure was greatest in trials ≥8 wk in duration [MD: 6.9 mm Hg (95% CI: 3.4, 10.3 mm Hg; P < 0.001) for systolic blood pressure and 5.6 mm Hg (95% CI: 2.5, 8.8 mm Hg; P = 0.0005) for diastolic blood pressure]. CONCLUSIONS Dietary sugars influence blood pressure and serum lipids. The relation is independent of effects of sugars on body weight. Protocols for this review were registered separately for effects of sugars on blood pressure and lipids in the PROSPERO International prospective register of systematic reviews as PROSPERO 2012: CRD42012002379 and 2012: CRD42012002437, respectively.

Comparison of high protein and high fiber weight-loss diets in women with risk factors for the metabolic syndrome: a randomized trial

BackgroundStudies have suggested that moderately high protein diets may be more appropriate than conventional low-fat high carbohydrate diets for individuals at risk of developing the metabolic syndrome and type 2 diabetes. However in most such studies sources of dietary carbohydrate may not have been appropriate and protein intakes may have been excessively high. Thus, in a proof-of-concept study we compared two relatively low-fat weight loss diets - one high in protein and the other high in fiber-rich, minimally processed cereals and legumes - to determine whether a relatively high protein diet has the potential to confer greater benefits.MethodsEighty-three overweight or obese women, 18-65 years, were randomized to either a moderately high protein (30% protein, 40% carbohydrate) diet (HP) or to a high fiber, relatively high carbohydrate (50% carbohydrate, > 35 g total dietary fiber, 20% protein) diet (HFib) for 8 weeks. Energy intakes were reduced by 2000 - 4000 kJ per day in order to achieve weight loss of between 0.5 and 1 kg per week.ResultsParticipants on both diets lost weight (HP: -4.5 kg [95% confidence interval (CI):-3.7, -5.4 kg] and HFib: -3.3 kg [95% CI: -4.2, -2.4 kg]), and reduced total body fat (HP: -4.0 kg [5% CI:-4.6, -3.4 kg] and HFib: -2.5 kg [95% CI: -3.5, -1.6 kg]), and waist circumference (HP: -5.4 cm [95% CI: -6.3, -4.5 cm] and HFib: -4.7 cm [95% CI: -5.8, -3.6 cm]), as well as total and LDL cholesterol, triglycerides, fasting plasma glucose and blood pressure. However participants on HP lost more body weight (-1.3 kg [95% CI: -2.5, -0.1 kg; p = 0.039]) and total body fat (-1.3 kg [95% CI: -2.4, -0.1; p = 0.029]). Diastolic blood pressure decreased more on HP (-3.7 mm Hg [95% CI: -6.2, -1.1; p = 0.005]).ConclusionsA realistic high protein weight-reducing diet was associated with greater fat loss and lower blood pressure when compared with a high carbohydrate, high fiber diet in high risk overweight and obese women.

The dynamic insulin sensitivity and secretion test--a novel measure of insulin sensitivity.

The objective was to validate the methodology for the dynamic insulin sensitivity and secretion test (DISST) and to demonstrate its potential in clinical and research settings. One hundred twenty-three men and women had routine clinical and biochemical measurements, an oral glucose tolerance test, and a DISST. For the DISST, participants were cannulated for blood sampling and bolus administration. Blood samples were drawn at t = 0, 10, 15, 25, and 35 minutes for measurement of glucose, insulin, and C-peptide. A 10-g bolus of intravenous glucose at t = 5 minutes and 1 U of intravenous insulin immediately after the t = 15 minute sample were given. Fifty participants also had a hyperinsulinemic-euglycemic clamp. Relationships between DISST insulin sensitivity (SI) and the clamp, and both DISST SI and secretion and other metabolic variables were measured. A Bland-Altman plot showed little bias in the comparison of DISST with the clamp, with DISST underestimating the glucose clamp by 0.1·10(-2)·mg·L·kg(-1)·min(-1)·pmol(-1) (90% confidence interval, -0.2 to 0). The correlation between SI as measured by DISST and the clamp was 0.82; the c unit for the receiver operating characteristic curve analysis for the 2 tests was 0.96. Metabolic variables showed significant correlations with DISST SI and the second phase of insulin release. The DISST also appears able to distinguish different insulin secretion patterns in individuals with identical SI values. The DISST is a simple, dynamic test that compares favorably with the clamp in assessing SI and allows simultaneous assessment of insulin secretion. The DISST has the potential to provide even more information about the pathophysiology of diabetes than more complicated tests.

The role of high-protein diets in body weight management and health

Studies examining the health benefits of high-protein diets typical of most affluent and many developing countries are not consistent. Prospective epidemiological studies relating dietary protein to clinical and metabolic endpoints suggest increased weight gain and increased risk of diabetes amongst those with a high protein intake and an increased risk of cancer with high intakes of red meat, but lower blood pressure and possibly a reduced risk of heart disease with higher protein intakes. The potential for high-protein diets to confer greater benefit than other diets has been examined using ad libitum and energy restricted diets. Of greatest interest have been the comparisons between high-protein and high-carbohydrate diets. Many trials have reported greater weight loss especially in the context of ad libitum diets over the short-to medium-term, sparing of lean body mass, lowering of triglyceride levels, improved HDL: total cholesterol ratio and improved glycaemic control. Limited data regarding insulin sensitivity are less consistent. A major difficulty in interpreting the results of these studies is that carbohydrate quality has not been taken into account. Furthermore, longer term comparisons of weight reducing diets differing in macronutrient composition have reported similar outcomes, suggesting that compliance is a more important consideration. Nevertheless dietary patterns with high-protein intakes are appropriate for weight reduction and weight maintenance and may be useful for those who have high triglyceride levels and other features of the metabolic syndrome.

Diet and diabetes revisited, yet again

Dietary modification has the potential to appreciably reduce the risk of progression of prediabetes to type 2 diabetes (T2D), with several high-profile randomized controlled trials (RCTs) conducted in persons of varying ethnicities in different countries that consistently show a halving of risk (1). The benefit appears to persist many years after the conclusion of the interventions (2). Medical nutrition therapy is the mainstay of treatment of T2D. Compliance with dietary advice results in improvement in glycemic control and reduction in cardiovascular risk regardless of duration of disease. A meaningful reduction in glycated hemoglobin after intensified nutrition therapy has been observed in patients with longstanding T2D whose oral hypoglycemic or insulin treatment had been optimized (3). Given that most people at risk of or with T2D are overweight or obese, it is hardly surprising that weight loss (typically 5% of initial body weight) has been the most consistent nutritionrelated determinant of positive outcomes (4). Reducing excess adiposity is the cornerstone of all nutrition recommendations for prevention and treatment of T2D. Two systematic reviews and meta-analyses published in this issue of the Journal relate to aspects of nutrition for which there is less universal agreement (5, 6). Livesey et al (6) explored whether there is a dose-response relation between dietary glycemic load (GL) and risk of developing T2D. The meta-analysis, which included 24 prospective cohort studies and 7.5 million person-years of follow-up, showed a relative risk for T2D of 1.45 (95% CI: 1.31, 1.61) for a 100-g increment in GL, a relation apparent at all doses of GL .95 g/2000 kcal. A further additional novel finding was that 97% of the heterogeneity between studies was explained by validity of the dietary instrument, sex (the association between GL and T2D was significant only in women), and ethnicity (the association was stronger in European Americans than in other ethnicities combined). The sex difference may be explained by sex differences in dietary behavior or standard of recording rather than inherent/genetic differences, and the more striking effect among European Americans may be explained by the fact that they constituted the substantial majority of the individuals included in the meta-analysis. Although we acknowledge that the impressive doseresponse effect provides strong support for the suggestion that dietary GL is a significant determinant of subsequent risk of developing T2D, we are not convinced that low GL should be a major defining feature of dietary advice aimed to reduce the risk of T2D. The authors acknowledge the imprecision of published glycemic index (GI) data from which dietary GL is calculated. Furthermore, GL was not a feature of the diets that were clearly shown in wellknown RCTs (the highest level of evidence in determining dietary recommendations) to reduce risk of progression to T2D. These diets were first and foremost designed to achieve weight loss with an emphasis on reduction in total and saturated fat and generous intakes of fruit, vegetables, whole-grain cereals, and dietary fiber. Undue emphasis on low-GI foods and dietary GL without clear advice on food choices could result in substantial intakes of foods (including functional foods) that are high in sugars (including high-fructose corn syrup) and/or fats and that are energy dense despite having a low GI. Nutritional recommendations for the ‘‘prevention’’ of T2D are most appropriately based on the results of the RCTs. A diet that is based on appropriate food choices is likely to have a GL of ,100 g/2000 kcal without specific advice in this regard. Ajala et al (5) have made a brave attempt to answer a rather more difficult question: whether any particular dietary pattern or macronutrient distribution is most suitable for inducing weight loss and improving glycemic control and lipid profile in people with T2D. They chose to examine the merits of low-carbohydrate, low-GI, high-fiber, high-protein, Mediterranean, vegetarian, and vegan diets and included in their review RCTs lasting for 6 mo in which one or more of these dietary approaches was compared with a control diet, the composition of which was not specified. On the basis of their review and meta-analysis, the authors conclude that the low-carbohydrate, low-GI, Mediterranean, and high-protein diets are effective in improving various markers of cardiovascular risk in people with diabetes and suggest that there may be a range of beneficial dietary options for those with T2D. How valid and novel are these conclusions? The authors acknowledge the potential confounding and heterogeneity that result from appreciable differences in macronutrient composition of the control diets, the fact that the

Authors' reply to Cottrell and Wittekind.

Our meta-analysis was mainly intended to determine the effect on body weight of increased or decreased intake of sugars or food and drink containing sugars in free living people.1 2 It was therefore appropriate to exclude studies in which changes in other dietary or exercise practices were recommended and to include studies …

A Spectrum of Dynamic Insulin Sensitivity Test Protocols

Background: Numerous tests have been developed to estimate insulin sensitivity (SI). However, most of the established tests are either too expensive for widespread application or do not yield reliable results. The dynamic insulin sensitivity and secretion test (DISST) uses assays of glucose, insulin, and C-peptide from nine samples to quantify SI and endogenous insulin secretion (UN ) at a comparatively low cost. The quick dynamic insulin sensitivity test has shown that the DISST SI values are robust to significant assay omissions. Methods: Eight DISST-based variations of the nine-sample assay regimen are proposed to investigate the effects of assay omission within the DISST-based framework. SI and UN were identified using the fully-sampled DISST and data from 218 nine-sample tests undertaken in 74 female individuals with elevated diabetes risk. This same data was then used with appropriate assay omissions to identify SI and UN with the eight DISST-based assay variations. Results: Median intraprocedure proportional difference between SI values from fully-sampled DISST and the DISST-based variants was in the range of −17.9 to 7.8%. Correlations were in the range of r = 0.71 to 0.92 with the highest correlations between variants with the greatest commonality with the nine-sample DISST. Metrics of UN correlated relatively well between tests when C−peptide was assayed (r = 0.72 to 1) but were sometimes not well estimated when samples were not assayed for C-peptide (r = −0.14 to 0.75). Conclusions: The DISST-based spectrum offers a series of tests with very distinct compromises of information yield, accuracy, assay cost, and clinical intensity. Thus, the spectrum of tests has the potential to enable researchers to better allocate funds by selecting an optimal test configuration for their particular application.

Co-design of mHealth Delivered Interventions: A Systematic Review to Assess Key Methods and Processes

Most mobile health (mHealth) programmes are designed with minimal input from target end users and are not truly personalised or adaptive to their specific and evolving needs. This review describes the methods and processes used in the co-design of mHealth interventions. Nine relevant studies of varying design were identified following searches of six academic databases. All employed co-design or participatory methods for the development of a health intervention delivered via a mobile device, with three focusing on health behaviour change (one on nutrition) and six on management of a health condition. Overall, six key phases of design and 17 different methods were used. Sufficiency of reporting was poor, and no study undertook a robust assessment of efficacy; these factors should be a focus for future studies. An opportunity exists to use co-design methods to develop acceptable and feasible mHealth interventions, especially to support improved nutrition and for minority and indigenous groups.

Estimating Free and Added Sugar Intakes in New Zealand

The reduction of free or added sugar intake (sugars added to food and drinks as a sweetener) is almost universally recommended to reduce the risk of obesity-related diseases and dental caries. The World Health Organisation recommends intakes of free sugars of less than 10% of energy intake. However, estimating and monitoring intakes at the population level is challenging because free sugars cannot be analytically distinguished from naturally occurring sugars and most national food composition databases do not include data on free or added sugars. We developed free and added sugar estimates for the New Zealand (NZ) food composition database (FOODfiles 2010) by adapting a method developed for Australia. We reanalyzed the 24 h recall dietary data collected for 4721 adults aged 15 years and over participating in the nationally representative 2008/09 New Zealand Adult Nutrition Survey to estimate free and added sugar intakes. The median estimated intake of free and added sugars was 57 and 49 g/day respectively and 42% of adults consumed less than 10% of their energy intake from free sugars. This approach provides more direct estimates of the free and added sugar contents of New Zealand foods than previously available and will enable monitoring of adherence to free sugar intake guidelines in future.