Sze Yen Tan

Long-term effects of increased dietary polyunsaturated fat from walnuts on metabolic parameters in type II diabetes.

Background/Objectives:Most dietary interventions have metabolic effects in the short term, but long-term effects may require dietary fat changes to influence body composition and insulin action. This study assessed the effect of sustained high polyunsaturated fatty acids (PUFA) intake through walnut consumption on metabolic outcomes in type II diabetes.Subjects/Methods:Fifty overweight adults with non-insulin-treated diabetes (mean age 54±8.7 years) were randomized to receive low-fat dietary advice ±30 g per day walnuts targeting weight maintenance (around 2000 kcal, 30% fat) for 1 year. Differences between groups were assessed by changes in anthropometric values (body weight, body fat, visceral adipose tissue) and clinical indicators of diabetes over treatment time using the general linear model.Results:The walnut group consumed significantly more PUFA than the control (P=0.035), an outcome attributed to walnut consumption (contributing 67% dietary PUFA at 12 months). Most of the effects were seen in the first 3 months. Despite being on weight maintenance diets, both groups sustained a 1–2 kg weight loss, with no difference between groups (P=0.680). Both groups showed improvements in all clinical parameters with significant time effects (P<0.004), bar triacylglycerol levels, but these were just above normal to begin with. The walnut group produced significantly greater reductions in fasting insulin levels (P=0.046), an effect seen largely in the first 3 months.Conclusions:Dietary fat can be manipulated with whole foods such as walnuts, producing reductions in fasting insulin levels. Long-term effects are also apparent but subject to fluctuations in dietary intake if not of the disease process.

Appetitive, dietary and health effects of almonds consumed with meals or as snacks: a randomized, controlled trial.

Background/Objectives:Snacks contribute toward a significant proportion of human total daily energy intake. This study investigated the effects of almonds, a satiating and nutrient-rich, common snack, on postprandial glycemia, appetite, short-term body weight and fasting blood parameters when consumed with meals or alone as a snack.Methods:This was a 4-week randomized, parallel-arm study that entailed consuming almonds (43 g/day) with breakfast (BF) or lunch (LN), alone as a morning (MS) or afternoon (AS) snack or no almonds (CL). Participants (N=137) with increased risk for type 2 diabetes completed an oral glucose tolerance test (OGTT) and acute-feeding session at baseline, followed by almond consumption for 4 weeks before repeating the OGTT and acute-feeding trials. Anthropometric, biochemical and appetite responses were assessed.Results:Almonds lowered serum glucose responses postprandially. Effects were most prominent in the snack groups. Almonds, consumed as snacks, also reduced hunger and desire to eat during the acute-feeding session. After 4 weeks, anthropometric measurements and fasting blood biochemistries did not differ from the control group or across intervention groups. Without specific guidance, daily energy intake was reduced to compensate for energy from the provided almonds. Dietary monounsaturated fat and α-tocopherol intakes were significantly increased in all almond groups.Conclusion:Almonds provide post-ingestive metabolic and appetitive benefits and did not increase the risk for weight gain. This suggests that almonds may be a healthful snack option.

A review of the effects of nuts on appetite, food intake, metabolism, and body weight

Tree nuts and peanuts are good sources of many nutrients and antioxidants, but they are also energy dense. The latter often limits intake because of concerns about their possible contribution to positive energy balance. However, evidence to date suggests that nuts are not associated with predicted weight gain. This is largely due to their high satiety value, leading to strong compensatory dietary responses, inefficiency in absorption of the energy they contain, a possible increment in resting energy expenditure, and an augmentation of fat oxidation. Preliminary evidence suggests that these properties are especially evident when they are consumed as snacks.

Relative Validity of 3 Accelerometer Models for Estimating Energy Expenditure During Light Activity

BACKGROUND With physical inactivity inextricably linked to the increasing prevalence of obesity, there is a need for validated methods that measure free-living energy expenditure (EE) within sedentary environments. While accelerometers enable these measurements, few studies have compared device accuracy in such settings. The aim of this study was to investigate the relative validity of the Actigraph, RT3 and SenseWear Armband (SWA). METHODS Twenty-three (11 male, 12 female) participants (age: 25.3 ± 6.3 yr; BMI: 22.6 ± 2.7) wore 3 accelerometers at designated sites during a 4-hour stay in the Whole Room Calorimeter (WRC). Participants performed 2 10-minute bouts of light-intensity exercise (stepping and stationary cycling) and engaged in unstructured sedentary activities. EE estimated by accelerometers was compared with WRC EE derived from measurements of gaseous exchange. RESULTS The Actigraph and SWA both accurately estimated EE during the stepping exercise. EE estimated by the RT3 during stepping was significantly lower than the WRC value (31.2% ± 15.6%, P < .001). All accelerometers underestimated cycling and unstructured activity EE over the trial period (P < .001). CONCLUSIONS The Actigraph and SWA are both valid tools for quantifying EE during light-intensity stepping. These results provide further valuable information on how accelerometer devices may be appropriately used.

Effects of fruit and vegetable, consumed in solid vs beverage forms, on acute and chronic appetitive responses in lean and obese adults.

Background:The effects of fruits and vegetables in solid vs beverage forms on human appetite and food intake, acutely and chronically, are unclear.Methods:This 21-week, randomized, crossover study assessed appetitive ratings following the inclusion of fruits and vegetables, in solid and beverage form, into the habitual diet of healthy lean (n=15) and overweight/obese (n=19) adults with low customary consumption. The primary acute outcomes were satiation (amount of challenge meal consumed), satiety (latency of subsequent eating event) and dietary compensation after a 400 kcal fruit preload. Ratings of appetite were also obtained before and after 8 weeks of required increased fruit and vegetable consumption (20% estimated energy requirement).Results:Acutely, overweight/obese participants reported smaller reductions of hunger after consuming the fruit preload in beverage compared with solid form (preload × form × body mass index effects, P=0.03). Participants also consumed significantly less of a challenge meal (in both gram and energy) after the ingestion of the solid fruit preload (P<0.005). However, the subsequent meal latency was not significantly different between the solid and the beverage fruit preloads. Total daily energy intake was significantly higher when the obese participants consumed the beverage fruit preload compared with the solid (P<0.001). Daily energy intake was markedly, but not significantly, higher among the lean with the beverage vs solid food form. Hunger and fullness ratings remained stable when participants consumed fruits and vegetables in solid or beverage form for 8 weeks each.Conclusion:Acute post-ingestive appetitive responses were weaker following consumption of fruits in beverage vs solid food forms. Consumption of beverage or solid fruit and vegetable food loads for 8 weeks did not chronically alter appetitive responses.

Protein leverage effects of beef protein on energy intake in humans

BACKGROUND The protein leverage hypothesis requires specific evidence that protein intake is regulated more strongly than energy intake. OBJECTIVE The objective was to determine ad libitum energy intake, body weight changes, appetite profile, and nitrogen balance in response to 3 diets with different protein-to-carbohydrate + fat ratios over 12 consecutive days, with beef as a source of protein. DESIGN A 3-arm, 12-d randomized crossover study was performed in 30 men and 28 women [mean ± SD age: 33 ± 16 y; body mass index (in kg/m²): 24.4 ± 4.0] with the use of diets containing 5%, 15%, and 30% of energy (En%) from protein, predominantly from beef. RESULTS Energy intake was significantly lower in the 30En%-protein condition (8.73 ± 1.93 MJ/d) than in the 5En%-protein (9.48 ± 1.67 MJ/d) and 15En%-protein (9.30 ± 1.62 MJ/d) conditions (P = 0.001), stemming largely from lower energy intake during meals (P = 0.001). Hunger (P = 0.001) and desire to eat (P = 0.001) ratings were higher and fullness ratings were lower (P = 0.001) in the 5En%-protein condition than in the 15En%-protein and 30En%-protein conditions. Nitrogen excretion was lower in the 5En%-protein condition (4.7 ± 1.5 g/24 h; P = 0.001) and was higher in the 30En%-protein condition (15.3 ± 8.7 g/24 h; P = 0.001) compared with the 15En%-protein condition (10.0 ± 5.2 g/24 h). Nitrogen balance was maintained in the 5En%-protein condition and was positive in the 15En%- and 30En%-protein conditions (P = 0.001). CONCLUSIONS Complete protein leverage did not occur because subjects did not consume to a common protein amount at the expense of energy balance. Individuals did underconsume relative to energy requirements from high-protein diets. The lack of support for protein leverage effects on a low-protein diet may stem from the fact that protein intake was sufficient to maintain nitrogen balance over the 12-d trial.

Energy Expenditure Does not Differ, but Protein Oxidation Rates Appear Lower in Meals Containing Predominantly Meat versus Soy Sources of Protein

Background: High protein meals produce 3 relevant effects in weight management: i) higher thermogenic cost, ii) enhanced fat oxidation, and iii) greater satiation. Pork has been reported to be more thermogenic than soy, suggesting meat protein may be superior to plant protein in a high-protein weight loss diet context. In this study, we aimed to compare the effects of high-protein meals using meat, dairy, and soy sources respectively. Methods: This crossover feeding trial measured energy expenditure, substrate oxidation, and satiety levels of 12 adults during 8-hour stays in a whole-room calorimeter. The 3 isoenergetic high-protein test meals (30% protein, 40% carbohydrate, 30% fat) contained predominantly meat, dairy, and soy protein. Results: There was no significant difference between meals for effects on energy expenditure (p = 0.987), carbohydrate oxidation (p = 0.951), and fat oxidation (p = 0.997). Protein oxidation was significantly lower in meals with predominantly meat compared to soy sources (p = 0.012). There was no significant difference between meals for reported satiety levels (p = 0.296). Conclusion: High-protein meals may be argued as beneficial for weight loss. Animal protein does not appear to offer superior energy expenditure effects, but there may be protein-sparing effects with meat, which may be beneficial in terms of retaining lean body mass.

Increased intake of dietary polyunsaturated fat does not promote whole body or preferential abdominal fat mass loss in overweight adults

Objective: There is evidence that increasing the proportion of polyunsaturated fatty acids (PUFA) in a diet can enhance the rate of fat oxidation acutely. Higher PUFA in a diet has also been associated with greater abdominal fat loss in longer term studies. This study aimed to investigate if higher PUFA intake would result in greater fat mass loss over a 12-week period, mainly from the abdominal region. Methods: Data at the 12-week time point from two weight loss studies, both comparing high PUFA versus low PUFA diets was, accessed for 141 overweight subjects from the same area. Specifically, data on anthropometric measurements (weight, height, BMI, body composition, waist and hip circumference, SAT, VAT) and dietary intake were analyzed. The relationship between fat mass and VAT changes was examined using a differential equation. Results: Energy consumption decreased significantly in both study groups. The low fat groups decreased total dietary fat while the HPUFA groups increased PUFA intake significantly. All anthropometric measurements reduced significantly over time but there was no difference between the two dietary groups. The relationship between fat mass and visceral adipose tissue (VAT) loss was allometric. Conclusion: A higher PUFA intake did not lead to greater fat mass loss and there was no additional preferential loss of VAT following higher PUFA consumption.

Do non-nutritive sweeteners influence acute glucose homeostasis in humans? A systematic review

The human body associates sensory cues with metabolic consequences. Exposure to sweet-tasting sugars - even in the absence of ingestion - triggers physiological responses that are associated with carbohydrate digestion, absorption and metabolism. These responses include the release of insulin and incretin hormones, which work to reduce blood glucose. For this reason, non-nutritive sweeteners (NNS) have been posited to trigger similar physiological responses and reduce postprandial blood glucose concentrations. The first part of this review presents a brief overview of sweet taste receptor activation in the oral cavity and gastrointestinal tract and the ensuing physiological responses related to glucose homeostasis. The second part of this review contains a systematic literature review that tested the hypothesis that NNS use improves glucose regulation postprandially. Studies were grouped based on sweet taste receptor stimulation paradigms, including pre-ingestive stimulation, ingestion of NNS alone, co-ingestion of NNS with foods, and using NNS as preloads to influence subsequent blood glucose excursions. In summary, the review found that NNS triggered physiological responses, albeit inconsistently, yet failed to significantly lower blood glucose levels in almost all studies.

Gross and relative energy cost of domestic household activities in Asian men

Background/Objectives:Obesity is on the rise and participation in exercise has declined. Domestic household activities may help meet the recommended daily physical activity levels. This study aimed to measure the energy costs of household activities among Asian males.Subjects/Methods:This was a randomised cross-over study conducted in a whole-body calorimeter. The energy costs of 14 domestic household activities, divided into two studies, were measured in 10 healthy Asian males. Participants’ weight, height, body composition and basal metabolic rate were measured on the first test visit. A standard breakfast was served and participants rested for an hour before the measurement of energy costs of domestic household activities. During the measurements, each activity was performed for 20 min, and participants rested for 30 min between activities.Results:The mean energy costs of domestic household activities ranged from 5.92 to 11.97 kJ/min, which were significantly different between activities (repeated measures analysis of variance, P<0.001). When expressed as metabolic equivalents (METS), all domestic household activities were classified as low-intensity physical activities. Actual METS (METSactual) were significantly different to standard METS of eight activities, which may be partly explained by the universal assumption of 3.5 ml O2/kg/min made during the calculation of METS in the Asian population.Conclusions:The energy costs of a range of domestic household activities reported in this study may assist in the planning of physical activities among Asians to meet national physical activity guidelines.