The First Step First Bite Program: guidance to increase physical activity and daily intake of low-glycemic index foods

Low glycaemic index diets for the prevention of cardiovascular disease

BACKGROUND

The glycaemic index (GI) is a physiological measure of the ability of a carbohydrate to affect blood glucose. Interest is growing in this area for the clinical management of people at risk of, or with, established cardiovascular disease. There is a need to review the current evidence from randomised controlled trials (RCTs) in this area. This is an update of the original review published in 2008.

OBJECTIVES

To assess the effect of the dietary GI on total mortality, cardiovascular events, and cardiovascular risk factors (blood lipids, blood pressure) in healthy people or people who have established cardiovascular disease or related risk factors, using all eligible randomised controlled trials.

SEARCH METHODS

We searched CENTRAL, MEDLINE, Embase and CINAHL in July 2016. We also checked reference lists of relevant articles. No language restrictions were applied.

SELECTION CRITERIA

We selected RCTs that assessed the effects of low GI diets compared to diets with a similar composition but a higher GI on cardiovascular disease and related risk factors. Minimum trial duration was 12 weeks. Participants included were healthy adults or those at increased risk of cardiovascular disease, or previously diagnosed with cardiovascular disease. Studies in people with diabetes mellitus were excluded.

DATA COLLECTION AND ANALYSIS

Two reviewers independently screened and selected studies. Two review authors independently assessed risk of bias, evaluated the overall quality of the evidence using GRADE, and extracted data following the Cochrane Handbook for Systematic Reviews of Interventions. We contacted trial authors for additional information. Analyses were checked by a second reviewer. Continuous outcomes were synthesized using mean differences and adverse events were synthesized narratively.

MAIN RESULTS

Twenty-one RCTs were included, with a total of 2538 participants randomised to low GI intervention (1288) or high GI (1250). All 21 included studies reported the effect of low GI diets on risk factors for cardiovascular disease, including blood lipids and blood pressure.Twenty RCTs (18 of which were newly included in this version of the review) included primary prevention populations (healthy individuals or those at high risk of CVD, with mean age range from 19 to 69 years) and one RCT was in those diagnosed with pre-existing CVD (a secondary prevention population, with mean age 26.9 years). Most of the studies did not have an intervention duration of longer than six months. Difference in GI intake between comparison groups varied widely from 0.6 to 42.None of the included studies reported the effect of low GI dietary intake on cardiovascular mortality and cardiovascular events such as fatal and nonfatal myocardial infarction, unstable angina, coronary artery bypass graft surgery, percutaneous transluminal coronary angioplasty, and stroke. The unclear risk of bias of most of the included studies makes overall interpretation of the data difficult. Only two of the included studies (38 participants) reported on adverse effects and did not observe any harms (low-quality evidence).

AUTHORS' CONCLUSIONS

There is currently no evidence available regarding the effect of low GI diets on cardiovascular disease events. Moreover, there is currently no convincing evidence that low GI diets have a clear beneficial effect on blood lipids or blood pressure parameters.

Enhancing Exercise Responsiveness across Prediabetes Phenotypes by Targeting Insulin Sensitivity with Nutrition

Exercise is a cornerstone therapy for chronic diseases related to multiorgan insulin resistance. However, not all individuals show the anticipated improvement in insulin sensitivity following exercise and these individuals are considered exercise resistant. Caloric restriction is an approach to enhance the effect of exercise on increasing peripheral and hepatic insulin sensitivity, as replenishing expended calories blunts these benefits. Alternatively, restricting carbohydrate intake, independent of energy balance, following exercise provides an additive effect on peripheral insulin sensitivity when compared to refeeding carbohydrate. Although carbohydrate composition modulates insulin sensitivity, few have studied effects of low glycemic index or whole-grain diets following exercise across prediabetes phenotypes on insulin sensitivity. Herein, we propose the novel hypothesis that the combination of individualized nutrition therapy and exercise should be based on the clinical pathology of prediabetes to overcome exercise resistance and improve responsiveness in people at risk for type 2 diabetes and cardiovascular disease.

Behavioral Programs for Type 2 Diabetes Mellitus: A Systematic Review and Network Meta-analysis

BACKGROUND

Behavioral programs may improve outcomes for individuals with type 2 diabetes mellitus, but there is a large diversity of behavioral interventions and uncertainty about how to optimize the effectiveness of these programs.

PURPOSE

To identify factors moderating the effectiveness of behavioral programs for adults with type 2 diabetes.

DATA SOURCES

6 databases (1993 to January 2015), conference proceedings (2011 to 2014), and reference lists.

STUDY SELECTION

Duplicate screening and selection of 132 randomized, controlled trials evaluating behavioral programs compared with usual care, active controls, or other behavioral programs.

DATA EXTRACTION

One reviewer extracted and another verified data. Two reviewers independently assessed risk of bias.

DATA SYNTHESIS

Behavioral programs were grouped on the basis of program content and delivery methods. A Bayesian network meta-analysis showed that most lifestyle and diabetes self-management education and support programs (usually offering ≥ 11 contact hours) led to clinically important improvements in glycemic control (≥ 0.4% reduction in hemoglobin A1c [HbA1c]), whereas most diabetes self-management education programs without added support-especially those offering 10 or fewer contact hours-provided little benefit. Programs with higher effect sizes were more often delivered in person than via technology. Lifestyle programs led to the greatest reductions in body mass index. Reductions in HbA1c seemed to be greater for participants with a baseline HbA1c level of 7.0% or greater, adults younger than 65 years, and minority persons (subgroups with ≥ 75% nonwhite participants).

LIMITATIONS

All trials had medium or high risk of bias. Subgroup analyses were indirect, and therefore exploratory. Most outcomes were reported immediately after the interventions.

CONCLUSION

Diabetes self-management education offering 10 or fewer hours of contact with delivery personnel provided little benefit. Behavioral programs seem to benefit persons with suboptimal or poor glycemic control more than those with good control.

PRIMARY FUNDING SOURCE

Agency for Healthcare Research and Quality. (PROSPERO registration number: CRD42014010515).

The transcultural diabetes nutrition algorithm: a canadian perspective

The Transcultural Diabetes Nutrition Algorithm (tDNA) is a clinical tool designed to facilitate implementation of therapeutic lifestyle recommendations for people with or at risk for type 2 diabetes. Cultural adaptation of evidence-based clinical practice guidelines (CPG) recommendations is essential to address varied patient populations within and among diverse regions worldwide. The Canadian version of tDNA supports and targets behavioural changes to improve nutritional quality and to promote regular daily physical activity consistent with Canadian Diabetes Association CPG, as well as channelling the concomitant management of obesity, hypertension, dyslipidemia, and dysglycaemia in primary care. Assessing glycaemic index (GI) (the ranking of foods by effects on postprandial blood glucose levels) and glycaemic load (GL) (the product of mean GI and the total carbohydrate content of a meal) will be a central part of the Canadian tDNA and complement nutrition therapy by facilitating glycaemic control using specific food selections. This component can also enhance other metabolic interventions, such as reducing the need for antihyperglycaemic medication and improving the effectiveness of weight loss programs. This tDNA strategy will be adapted to the cultural specificities of the Canadian population and incorporated into the tDNA validation methodology.

Exercise training with weight loss and either a high- or low-glycemic index diet reduces metabolic syndrome severity in older adults

BACKGROUND

The efficacy of combining carbohydrate quality with exercise on metabolic syndrome risk is unclear. Thus, we determined the effects of exercise training with a low (LoGIx)- or high (HiGIx)-glycemic index diet on the severity of the metabolic syndrome (Z-score).

METHODS

Twenty-one adults (66.2±1.1 years; BMI=35.3±0.9 kg/m2) with the metabolic syndrome were randomized to 12 weeks of exercise (60 min/day for 5 days/week at about 85% HRmax) and provided a LoGIx (n=11) or HiGIx (n=10) diet. Z-scores were determined from: blood pressure, triglycerides (TGs), high-density lipoproteins (HDLs), fasting plasma glucose (FPG), and waist circumference (WC) before and after the intervention. Body composition, aerobic fitness, insulin resistance, and nonesterfied fatty acid (NEFA) suppression were also assessed.

RESULTS

LoGIx and HiGIx diets decreased body mass and insulin resistance and increased aerobic fitness comparably (p<0.05). LoGIx and HiGIx diets decreased the Z-score similarly as each intervention decreased blood pressure, TGs, FPG and WC (p<0.05). The HiGIx diet tended to suppress NEFA during insulin stimulation compared with the LoGIx diet (p=0.06).

CONCLUSIONS

Our findings highlight that exercise with weight loss reduces the severity of the metabolic syndrome whether individuals were randomized to a HiGIx or a LoGIx diet.

New perspectives on nutritional interventions to augment lipid utilisation during exercise

The enhancement of fat oxidation during exercise is an aim for both recreational exercising individuals and endurance athletes. Nutritional status may explain a large part of the variation in maximal rates of fat oxidation during exercise. This review reveals novel insights into nutritional manipulation of substrate selection during exercise, explaining putative mechanisms of action and evaluating the current evidence. Lowering the glycaemic index of the pre-exercise meal can enhance lipid utilisation by up to 100 % through reduced insulin concentrations, although its application may be restricted to specific training sessions rather than competition. Chronic effects of dietary glycaemic index are less clear and warrant future study before firm recommendations can be made. A flurry of recent advances has overthrown the conventional view of l-carnitine supplementation, with skeletal muscle uptake possible under certain dietary conditions and providing a strategy to influence energy metabolism in an exercise intensity-dependent manner. Use of non-carbohydrate nutrients to stimulate muscle l-carnitine uptake may prove more beneficial for optimising lipid utilisation, but this requires more research. Studies investigating fish oil supplementation on fat oxidation during exercise are conflicting. In spite of some strong putative mechanisms, the only crossover trial showed no significant effect on lipid use during exercise. Ca may increase NEFA availability although it is not clear whether these effects occur. Ca and caffeine can increase NEFA availability under certain circumstances which could theoretically enhance fat oxidation, yet strong experimental evidence for this effect during exercise is lacking. Co-administration of nutrients to maximise their effectiveness needs further investigation.

How many steps/day are enough? For older adults and special populations

Older adults and special populations (living with disability and/or chronic illness that may limit mobility and/or physical endurance) can benefit from practicing a more physically active lifestyle, typically by increasing ambulatory activity. Step counting devices (accelerometers and pedometers) offer an opportunity to monitor daily ambulatory activity; however, an appropriate translation of public health guidelines in terms of steps/day is unknown. Therefore this review was conducted to translate public health recommendations in terms of steps/day. Normative data indicates that 1) healthy older adults average 2,000-9,000 steps/day, and 2) special populations average 1,200-8,800 steps/day. Pedometer-based interventions in older adults and special populations elicit a weighted increase of approximately 775 steps/day (or an effect size of 0.26) and 2,215 steps/day (or an effect size of 0.67), respectively. There is no evidence to inform a moderate intensity cadence (i.e., steps/minute) in older adults at this time. However, using the adult cadence of 100 steps/minute to demark the lower end of an absolutely-defined moderate intensity (i.e., 3 METs), and multiplying this by 30 minutes produces a reasonable heuristic (i.e., guiding) value of 3,000 steps. However, this cadence may be unattainable in some frail/diseased populations. Regardless, to truly translate public health guidelines, these steps should be taken over and above activities performed in the course of daily living, be of at least moderate intensity accumulated in minimally 10 minute bouts, and add up to at least 150 minutes over the week. Considering a daily background of 5,000 steps/day (which may actually be too high for some older adults and/or special populations), a computed translation approximates 8,000 steps on days that include a target of achieving 30 minutes of moderate-to-vigorous physical activity (MVPA), and approximately 7,100 steps/day if averaged over a week. Measured directly and including these background activities, the evidence suggests that 30 minutes of daily MVPA accumulated in addition to habitual daily activities in healthy older adults is equivalent to taking approximately 7,000-10,000 steps/day. Those living with disability and/or chronic illness (that limits mobility and or/physical endurance) display lower levels of background daily activity, and this will affect whole-day estimates of recommended physical activity.

A behavioural intervention incorporating specific glycaemic index goals improves dietary quality, weight control and glycaemic control in adults with type 2 diabetes

OBJECTIVE

A lower glycaemic index (GI) diet is associated with a reduction in glycosylated Hb (HbA(1c)) in people with diabetes. Yet, little research has been conducted to determine the effects of specific goals regarding consumption of low GI (LGI) foods on diabetes outcomes. The present study evaluated a behavioural intervention on dietary intake, weight status and HbA(1c), which included a goal to consume either six or eight servings of LGI foods daily.

DESIGN

A parallel two-group design was used. Following the 5-week intervention, participants were randomly assigned to the group of six (n 15) or eight (n 20) servings of LGI foods daily and followed up for 8 weeks. Dietary intake was assessed using the mean of 4 d food records.

SETTING

A metropolitan community in the USA.

SUBJECTS

Individuals aged 40-65 years with type 2 diabetes of ≥1 year and HbA(1c) ≥ 7·0 % were eligible.

RESULTS

There was no significant difference between goal difficulty groups with regard to GI servings at the end of the study. However, mean consumption of LGI foods increased by 2·05 (SE 0·47) and 1·65 (SE 0·40) servings per 4184 kJ in the six (P < 0·001) and eight (P < 0·001) LGI serving groups, respectively. For all participants combined, there were significant decreases in mean HbA(1c) (-0·58 (SE 0·21) %; P = 0·01), weight (-2·30 (SE 0·78) kg; P = 0·01), BMI (-0·80 (SE 0·29) kg/m(2); P = 0·01) and waist circumference (-2·36 (SE 0·81) cm; P = 0·01).

CONCLUSIONS

An intervention including a specific goal to consume six to eight servings of LGI foods daily can improve diabetes outcomes. Clinicians should help patients set specific targets for dietary change and identify ways of achieving those goals.

A low-glycemic index diet combined with exercise reduces insulin resistance, postprandial hyperinsulinemia, and glucose-dependent insulinotropic polypeptide responses in obese, prediabetic humans

BACKGROUND

The optimal lifestyle intervention that reverses diabetes risk factors is not known.

OBJECTIVE

We examined the effect of a low-glycemic index (GI) diet and exercise intervention on glucose metabolism and insulin secretion in obese, prediabetic individuals.

DESIGN

Twenty-two participants [mean ± SEM age: 66 ± 1 y; body mass index (in kg/m(2)): 34.4 ± 0.8] underwent a 12-wk exercise-training intervention (1 h/d for 5 d/wk at ≈ 85% of maximum heart rate) while randomly assigned to receive either a low-GI diet (LoGIX; 40 ± 0.3 units) or a high-GI diet (HiGIX; 80 ± 0.6 units). Body composition (measured by using dual-energy X-ray absorptiometry and computed tomography), insulin sensitivity (measured with a hyperinsulinemic euglycemic clamp with [6,6-(2)H(2)]-glucose), and oral glucose-induced insulin and incretin hormone secretion were examined.

RESULTS

Both groups lost equal amounts of body weight (-8.8 ± 0.9%) and adiposity and showed similar improvements in peripheral tissue (+76.2 ± 14.9%) and hepatic insulin sensitivity (+27.1 ± 7.1%) (all P < 0.05). However, oral glucose-induced insulin secretion was reduced only in the LoGIX group (6.59 ± 0.86 nmol in the prestudy compared with 4.70 ± 0.67 nmol in the poststudy, P < 0.05), which was a change related to the suppressed postprandial response of glucose-dependent insulinotropic polypeptide. When corrected for changes in β cell glucose exposure, changes in insulin secretion were attenuated in the LoGIX group but became significantly elevated in the HiGIX group.

CONCLUSIONS

Although lifestyle-induced weight loss improves insulin resistance in prediabetic individuals, postprandial hyperinsulinemia is reduced only when a low-GI diet is consumed. In contrast, a high-GI diet impairs pancreatic β cell and intestinal K cell function despite significant weight loss. These findings highlight the important role of the gut in mediating the effects of a low-GI diet on type 2 diabetes risk reduction.