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Latest Paper:
Long-term effects of a very low-carbohydrate diet and a low-fat diet on mood and cognitive function.
Commonwealth Scientific and Industrial Research Organisation-Food and Nutritional Sciences, PO Box 10041, Adelaide, BC, South Australia 5000. grant.brinkworth@csiro.au
BACKGROUND: Very low-carbohydrate (LC) diets are often used to promote weight loss, but the long-term effects on psychological function remain unknown. METHODS: A total of 106 overweight and obese participants (mean [SE] age, 50. [ .8] years; mean [SE] body mass index [calculated as weight in kilograms divided by height in meters squared], 33.7 [ .4]) were randomly assigned either to an energy-restricted (approximately 1433-1672 kcal [to convert to kilojoules, multiply by 4.186]), planned isocaloric, very low-carbohydrate, high-fat (LC) diet or to a high-carbohydrate, low-fat (LF) diet for 1 year. Changes in body weight, psychological mood and well-being (Profile of Mood States, Beck Depression Inventory, and Spielberger State Anxiety Inventory scores), and cognitive functioning (working memory and speed of processing) were assessed. RESULTS: By 1 year, the overall mean (SE) weight loss was 13.7 (1.8) kg, with no significant difference between groups (P =.26). Over the course of the study, there were significant time x diet interactions for Spielberger State Anxiety Inventory, Beck Depression Inventory, and Profile of Mood States scores for total mood disturbance, anger-hostility, confusion-bewilderment, and depression-dejection (P <.05) as a result of greater improvements in these psychological mood states for the LF diet compared with the LC diet. Working memory improved by 1 year (P <.001 for time), but speed of processing remained largely unchanged, with no effect of diet composition on either cognitive domain. CONCLUSIONS: Over 1 year, there was a favorable effect of an energy-restricted LF diet compared with an isocaloric LC diet on mood state and affect in overweight and obese individuals. Both diets had similar effects on working memory and speed of processing. Trial Registration anzctr.org.au Identifier: 12606000203550.
This study aimed to investigate the effects of prescriptive lifestyle advice with quantifiable dietary and physical goals compared to general lifestyle advice on weight and psychological outcomes in young women with overweight or obesity. A total of 203 women (body mass index 33.3+/- .3, age 28+/- .3 years) received either prescriptive or general lifestyle advice for weight loss over 12 weeks. Linear mixed models found that the prescriptive lifestyle advice group had significantly greater weight loss (4.2+/- .4 kg vs .6+/- .2 kg, P< .001) compared to the general lifestyle advice group. However, the prescriptive lifestyle advice group also had greater attrition (48% vs 31%, P< .05) compared to the general lifestyle advice group. Linear mixed models found that the prescriptive lifestyle advice group had greater improvement in psychological distress (-3. +/- .04 vs -1.1+/- .01, P< .05) and in self-esteem (3.2+/- .8 vs - .04+/- .04, P< .001) compared to the general lifestyle advice group. Changes in psychological distress and self-esteem remained significantly different between groups after correcting for weight loss. Food cravings decreased significantly over time without group differences (P< .001 for time). Weight locus of control remained unchanged in either group (P> .05). Drop-outs had greater baseline psychological distress (15.1+/- .7 vs 12.5+/- .4, P< .01) and higher food cravings (2.42+/- .07 vs 2.24+/- .05, P= .049) compared to completers. In conclusion, a prescriptive approach is associated with greater weight loss and greater improvements in psychological outcomes in young women compared to general lifestyle advice. However, these quantitative targets should be accompanied with qualitative advice on how they could be met in a variety of circumstances.
Discipline of Physiology, School of Molecular and Biomedical Science, Adelaide University, SA 5000, Australia; CSIRO Human Nutrition, P.O. Box 10041, Adelaide BC, SA 5000, Australia.
BACKGROUND AND AIM: Very low carbohydrate ad libitum diets have been shown to enhance weight loss without increasing cardiometabolic risk factors but no kilojoule-controlled trials have been conducted relative to no intervention. The aim of this study was to compare the changes in weight and other cardiovascular risk factors in 3 isocaloric energy-restricted diets to no-intervention control after 1 year. METHODS AND RESULTS: One hundred and thirteen subjects (age 47+/-10 years, BMI 32+/-6kg/m(2) with one additional cardiovascular risk factor) were randomly allocated to one of three isocaloric diets (VLC-very low carbohydrate, 60% fat, 4% carbohydrate, n=30; VLF-very low fat, 10% fat, n=30; HUF-high unsaturated fat, 30% fat, n=30) with intensive support for 3 months followed by minimal support for 12 months compared to a control group (no intervention, n=23). The estimated weight change was -3. +/- .2kg for VLC,-2. +/- .1kg for VLF,-3.7+/- .01kg for HUF and .8+/- .5kg for controls (P= .065). After correcting for baseline values, decreases in body weight and diastolic blood pressure in the diet groups (-2.9+/-5.2) were significantly different to the increase in the control group ( .8+/-5. )(P< .05). No differences in cardiovascular risk factors were observed between the diet groups. CONCLUSION: Significant cardiometabolic risk factor reduction was observed equally with VLC, VLF and HUF diets after 15 months, compared to an exacerbation of risk factors in the control group. At a modest level of adherence, 3 months of intensive support on these dietary patterns confer an improvement in cardiometabolic profile compared to no dietary intervention after 15 months.
Effects of a Low Carbohydrate Weight Loss Diet on Exercise Capacity and Tolerance in Obese Subjects.
Preventative Health Flagship, Commonwealth Scientific and Industrial Research Organisation-Human Nutrition, Adelaide, South Australia, Australia.
Dietary restriction and increased physical activity are recommended for obesity treatment. Very low carbohydrate diets are used to promote weight loss, but their effects on physical function and exercise tolerance in overweight and obese individuals are largely unknown. The aim of this study was to compare the effects of a very low carbohydrate, high fat (LC) diet with a conventional high carbohydrate, low fat (HC) diet on aerobic capacity, fuel utilization during submaximal exercise, perceived exercise effort (RPE) and muscle strength. Sixty subjects (age: 49.2 +/- 1.2 years; BMI: 33.6 +/- .5 kg/m(2)) were randomly assigned to an energy restricted (~6-7 MJ, 30% deficit), planned isocaloric LC or HC for 8 weeks. At baseline and week 8, subjects performed incremental treadmill exercise to exhaustion and handgrip and isometric knee extensor strength were assessed. Weight loss was greater in LC compared with HC (8.4 +/- .4% and 6.7 +/- .5%, respectively; P = .01 time x diet). Peak oxygen uptake and heart rate were unchanged in both groups (P > .17). Fat oxidation increased during submaximal exercise in LC but not HC (P < .001 time x diet effect). On both diets, perception of effort during submaximal exercise and handgrip strength decreased (P </= .03 for time), but knee extensor strength remained unchanged (P > .25). An LC weight loss diet shifted fuel utilization toward greater fat oxidation during exercise, but had no detrimental effect on maximal or submaximal markers of aerobic exercise performance or muscle strength compared with an HC diet. Further studies are required to determine the interaction of LC diets with regular exercise training and the long-term health effects.Obesity (2009) doi:10.1038/oby.2008.559.
CSIRO Human Nutrition and Food Science Australia, Adelaide, South Australia, Australia. nathan.o'callaghan@csiro.au
Telomere shortening may cause genome instability and is an initiating event in colorectal cancer (CRC). Obesity is associated with reduced telomere length in lymphocytes and is a risk factor for CRC, but the impact of obesity on telomere length in the rectal mucosa is unknown. The purpose of this study was to investigate the effect of weight loss, induced by calorie-restricted diets, on telomere length in the rectal mucosa of obese men. Midrectal biopsies were collected by sigmoidoscopy at three time points (at weeks , 12, and 52) during a programmed weight loss intervention. Weight was reduced by an average of 10.6 kg across the study. Telomere length, measured by quantitative real-time PCR (qPCR), was negatively correlated with body mass index (BMI)(r =- .13, p = .05) at baseline (n = 54) and increased at week 12 (four-fold increase) and week 52 (10-fold increase)(analysis of covariance [ANCOVA] p = .01, n = 12). Abasic sites in DNA decreased at week 12 (30% decrease) and week 52 (65% decrease)(analysis of variance [ANOVA] p = .02). Furthermore, gain of telomere length appeared to be greater if more weight and body fat was lost (r =- .65, p = .01 and r =- .56, p = .01, respectively). These results suggest that weight loss by caloric-restricted diets may contribute to the prevention of telomere shortening and DNA base damage, which are important initiating events in carcinogenesis.
Jing Ma,
Julie E Stevens,
Kimberly Cukier,
Anne F Maddox,
Judith M Wishart,
Karen L Jones,
Peter M Clifton,
Michael Horowitz,
Christopher K Rayner
Discipline of Medicine, University of Adelaide, Royal Adelaide Hospital, Adelaide, Australia.
Objective: We evaluated whether a whey 'preload' could slow gastric emptying, stimulate incretin hormones, and attenuate postprandial glycemia in type 2 diabetes. Research Design and Methods: 8 type 2 patients ingested 350mL beef soup, 30min before a potato meal; 55g whey was added either to the soup ('whey preload'), or potato ('whey in meal'), or 'no whey' was given. Results: Gastric emptying was slowest after the 'whey preload'(P< .0005). The incremental area under the blood glucose curve was less after the 'whey preload' and 'whey in meal' than 'no whey'(P< .005). Plasma glucose-dependent insulinotropic polypeptide, insulin and cholecystokinin concentrations were higher on both whey days than after 'no whey', whereas glucagon-like peptide-1 was greatest after the 'whey preload'(P< .05). Conclusions: Whey protein consumed before a carbohydrate meal can stimulate insulin and incretin hormone secretion, and slow gastric emptying, leading to marked reduction in postprandial glycemia in type 2 diabetes.
Discipine of Physiology, School of Molecular and Biomedical Science, Adelaide University, SA 5000; CSIRO Human Nutrition, Adelaide, SA 5000.
Reproductive disorders and psychological distress are common co-morbidities of obesity in young women. Psychological and reproductive disturbances may also be associated with increased food cravings but the relationships between these factors have not been explored. This study aimed to explore the pattern of food cravings and to determine the relationship between psychological distress, reproductive health and food cravings in overweight and obese young women using baseline data in a weight loss trial. A total of 198 young women were included in this analysis (BMI 33.3+ .3 kg/m(2), age 28+ .3 years). The most frequently craved food item was chocolate (3.9+ .08 i.e. sometimes-often). The most frequently craved food categories were fast foods (2.6+ .07) and sweets (2.5+ .05). Psychological distress was significantly correlated with food cravings (R(2)= .18, P< .05). High fat (r= .2), sweets (r= .17) and overall cravings (r= .20) were significantly correlated with energy intake (P< .05). Psychological distress did not correlate with energy intake (P> .05). Participants with menstrual disturbances had greater fast food cravings independent of age, BMI and PCOS status (P< .05). Participants with hyperandrogenemia had greater high fat food cravings independent of age, BMI and PCOS status (P< .01). Energy intake did not differ with menstrual disturbances or hyperandrogenemia (P> .05). These results suggest that psychological distress, hyperandrogenemia and menstrual disturbances are associated with greater food cravings. Further investigations are required to elucidate the relationship between hyperandrogenemia and food cravings in young women.
BACKGROUND: Long-term weight loss and cardiometabolic effects of a very-low-carbohydrate, high-saturated-fat diet (LC) and a high-carbohydrate, low-fat diet (LF) have not been evaluated under isocaloric conditions. OBJECTIVE: The objective was to compare an energy-controlled LC diet with an LF diet at 1 y. DESIGN: Men and women (n = 118) with abdominal obesity and at least one additional metabolic syndrome risk factor were randomly assigned to either an energy-restricted ( approximately 6-7 MJ) LC diet (4%, 35%, and 61% of energy as carbohydrate, protein, and fat, respectively) or an isocaloric LF diet (46%, 24%, and 30% of energy as carbohydrate, protein, and fat, respectively) for 1 y. Weight, body composition, and cardiometabolic risk markers were assessed. RESULTS: Sixty-nine participants (59%) completed the trial: 33 in the LC group and 36 in the LF group. Both groups lost similar amounts of weight (LC:-14.5 +/- 1.7 kg; LF:-11.5 +/- 1.2 kg; P = .14, time x diet) and body fat (LC: -11.3 +/- 1.5 kg; LF:-9.4 +/- 1.2 kg; P = .30). Blood pressure, fasting glucose, insulin, insulin resistance, and C-reactive protein decreased independently of diet composition. Compared with the LF group, the LC group had greater decreases in triglycerides (- .36 +/- .15 mmol/L; 95% CI:- .67,- .05 mmol/L; P = .011), increases in HDL cholesterol ( .23 +/- .09 mmol/L; 95% CI: .06, .40 mmol/L; P = .018) and LDL cholesterol ( .6 +/- .2 mmol/L; 95% CI: .2, 1. mmol/L; P = .001), and a greater but nonsignificant increase in apolipoprotein B ( .08 +/- .04 g/L; 95% CI:- .004, .171 g/L; P = .17). CONCLUSIONS: Under planned isoenergetic conditions, as expected, both dietary patterns resulted in similar weight loss and changes in body composition. The LC diet may offer clinical benefits to obese persons with insulin resistance. However, the increase in LDL cholesterol with the LC diet suggests that this measure should be monitored. This trial was registered with the Australian New Zealand Clinical Trials Registry at http://www.anzctr.org.au as ACTR 12606000203550.
Australian Technology Network Centre for Metabolic Fitness and Nutritional Physiology Research Centre, Sansom Institute for Health Research, University of South Australia, Adelaide 5001, Australia.
BACKGROUND Anti-Müllerian hormone (AMH) has been proposed as a clinical predictor of improvements in reproductive function following weight loss in overweight and obese women with polycystic ovary syndrome (PCOS). This study aimed to assess whether baseline and/or change in AMH levels with weight loss predict improvements in reproductive function in overweight and obese women with PCOS. METHODS Fifty-two overweight and obese women with PCOS and reproductive impairment (age 29.8 +/- .8 years, BMI 36.5 +/- .7 kg/m(2)) followed a 20-week weight loss programme. AMH, weight, menstrual cyclicity and ovulatory function were assessed at baseline and post-intervention. RESULTS Participants who responded with improvements in reproductive function (n = 26) had lower baseline AMH levels (23.5 +/- 3.7 versus 32.5 +/- 2.9 pmol/l; P = .03) and experienced greater weight loss (-11.7 +/- 1.2 versus -6.4 +/- .9 kg; P = .001) compared with those who did not respond (n = 26). Logistic regression analysis showed that weight loss and baseline AMH were independently related to improvements in reproductive function (P = .002 and P = .013, respectively). AMH levels did not change with weight loss in both responders and non-responders. CONCLUSIONS In overweight and obese women with PCOS and reproductive dysfunction, a 20-week weight loss intervention resulted in improvements in reproductive function but no change in AMH levels. Clinical Trials Registration Number: ACTRN12606000198527.
Effects of a Low Carbohydrate Weight Loss Diet on Exercise Capacity and Tolerance in Obese Subjects.
Preventative Health Flagship, Commonwealth Scientific and Industrial Research Organisation-Human Nutrition, Adelaide, South Australia, Australia.
Dietary restriction and increased physical activity are recommended for obesity treatment. Very low carbohydrate diets are used to promote weight loss, but their effects on physical function and exercise tolerance in overweight and obese individuals are largely unknown. The aim of this study was to compare the effects of a very low carbohydrate, high fat (LC) diet with a conventional high carbohydrate, low fat (HC) diet on aerobic capacity, fuel utilization during submaximal exercise, perceived exercise effort (RPE) and muscle strength. Sixty subjects (age: 49.2 +/- 1.2 years; BMI: 33.6 +/- .5 kg/m(2)) were randomly assigned to an energy restricted (~6-7 MJ, 30% deficit), planned isocaloric LC or HC for 8 weeks. At baseline and week 8, subjects performed incremental treadmill exercise to exhaustion and handgrip and isometric knee extensor strength were assessed. Weight loss was greater in LC compared with HC (8.4 +/- .4% and 6.7 +/- .5%, respectively; P = .01 time x diet). Peak oxygen uptake and heart rate were unchanged in both groups (P > .17). Fat oxidation increased during submaximal exercise in LC but not HC (P < .001 time x diet effect). On both diets, perception of effort during submaximal exercise and handgrip strength decreased (P </= .03 for time), but knee extensor strength remained unchanged (P > .25). An LC weight loss diet shifted fuel utilization toward greater fat oxidation during exercise, but had no detrimental effect on maximal or submaximal markers of aerobic exercise performance or muscle strength compared with an HC diet. Further studies are required to determine the interaction of LC diets with regular exercise training and the long-term health effects.Obesity (2009) doi:10.1038/oby.2009.134.
