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Biomedical subjects

Marlene M Most

Publications and source records attributed to Marlene M Most.

14 recordsLinked to original sources
PubMed2006

Effect of 6-month calorie restriction on biomarkers of longevity, metabolic adaptation, and oxidative stress in overweight individuals: a randomized controlled trial.

CONTEXT: Prolonged calorie restriction increases life span in rodents. Whether prolonged calorie restriction affects biomarkers of longevity or markers of oxidative stress, or reduces metabolic rate beyond that expected from reduced metabolic mass, has not been investigated in humans. OBJECTIVE: To examine the effects of 6 months of calorie restriction, with or without exercise, in overweight, nonobese (body mass index, 25 to <30) men and women. DESIGN, SETTING, AND PARTICIPANTS: Randomized controlled trial of healthy, sedentary men and women (N = 48) conducted between March 2002 and August 2004 at a research center in Baton Rouge, La. INTERVENTION: Participants were randomized to 1 of 4 groups for 6 months: control (weight maintenance diet); calorie restriction (25% calorie restriction of baseline energy requirements); calorie restriction with exercise (12.5% calorie restriction plus 12.5% increase in energy expenditure by structured exercise); very low-calorie diet (890 kcal/d until 15% weight reduction, followed by a weight maintenance diet). MAIN OUTCOME MEASURES: Body composition; dehydroepiandrosterone sulfate (DHEAS), glucose, and insulin levels; protein carbonyls; DNA damage; 24-hour energy expenditure; and core body temperature. RESULTS: Mean (SEM) weight change at 6 months in the 4 groups was as follows: controls, -1.0% (1.1%); calorie restriction, -10.4% (0.9%); calorie restriction with exercise, -10.0% (0.8%); and very low-calorie diet, -13.9% (0.7%). At 6 months, fasting insulin levels were significantly reduced from baseline in the intervention groups (all P<.01), whereas DHEAS and glucose levels were unchanged. Core body temperature was reduced in the calorie restriction and calorie restriction with exercise groups (both P<.05). After adjustment for changes in body composition, sedentary 24-hour energy expenditure was unchanged in controls, but decreased in the calorie restriction (-135 kcal/d [42 kcal/d]), calorie restriction with exercise (-117 kcal/d [52 kcal/d]), and very low-calorie diet (-125 kcal/d [35 kcal/d]) groups (all P<.008). These "metabolic adaptations" (~ 6% more than expected based on loss of metabolic mass) were statistically different from controls (P<.05). Protein carbonyl concentrations were not changed from baseline to month 6 in any group, whereas DNA damage was also reduced from baseline in all intervention groups (P <.005). CONCLUSIONS: Our findings suggest that 2 biomarkers of longevity (fasting insulin level and body temperature) are decreased by prolonged calorie restriction in humans and support the theory that metabolic rate is reduced beyond the level expected from reduced metabolic body mass. Studies of longer duration are required to determine if calorie restriction attenuates the aging process in humans. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT00099151.

Adult↗
PubMed2005

Dietary adherence in well-controlled feeding studies.

In well-controlled feeding studies, participants are expected to adhere to a strict diet by consuming only and all foods provided by the research kitchen. They may find adherence more of a challenge with certain study design features. To assess this we mailed a post-study anonymous questionnaire to participants who had completed one of eight controlled feeding studies at the Pennington Biomedical Research Center, Baton Rouge, LA. Of the 154 respondents, more than 90% always or usually adhered to the diet. Of those who did not adhere, many deviated fewer than four times. Eating all of the foods provided was a greater challenge than refraining from eating foods not allowed. Diet assignment, the allowance of alcohol, and a self-selected Saturday meal affected adherence. The results of this research may be useful in designing controlled feeding studies. Our data indicate that diet adherence is good, and because deviations are few, they are unlikely to jeopardize study results.

Adult↗
PubMed2005

Comparison of the acute response to meals enriched with cis- or trans-fatty acids on glucose and lipids in overweight individuals with differing FABP2 genotypes.

Trans-fatty acids have been implicated as a risk factor for cardiovascular disease and diabetes. In addition, a polymorphism at codon 54 (Ala54Thr) in the fatty acid-binding protein 2 (FABP2) gene has been suggested to modify an interaction between dietary fat and insulin sensitivity. We examined the postprandial metabolic profiles after meals enriched with C18:1trans- relative to a similar meal with C18:1cis-fatty acid in individuals who were either FABP2 Ala54 homozygotes or Thr54 carriers. Moderately overweight men and women ate 2 breakfast test meals, separated by 1 week, each providing 40% of their daily energy requirement and containing 50% of energy as fat. In one meal, 10% of energy was from C18:1trans, and in the other meal, the C18:1trans was replaced with C18:1cis. Metabolic parameters were assessed during an 8-hour period. Insulin and C-peptide levels increased more after the C18:1trans meal, and this was associated with a greater fall in free fatty acids. Postprandial glucose levels and oxidation of fatty acids and carbohydrate were not different between the 2 test meals. The Thr54 allele for FABP2 increased the rise in postprandial glucose but not triacylglycerols. Fractional triacylglycerol synthetic rates were higher after consumption of the C18:1trans meal relative to the C18:1cis meal only in Thr54 carriers. These data show that a single meal enriched with C18:1trans-fatty acids can significantly increase insulin resistance, and that in the presence of the FABP2 Thr54 allele, may contribute to increased partitioning of glucose to triacylglycerols and insulin resistance.

Adult↗
PubMed2005

Rice bran oil, not fiber, lowers cholesterol in humans.

BACKGROUND: The cholesterol-lowering abilities of rice bran's fiber and oil apart from its fatty acid composition remain unclear. OBJECTIVE: The objective of the study was to assess the effects of defatted rice bran and rice bran oil in an average American diet on blood lipids in moderately hypercholesterolemic persons. DESIGN: Study 1 used a parallel-arm design. Twenty-six healthy volunteers consumed a diet with 13-22 g dietary fiber/d for 3 wk, and then 13 of the volunteers were switched to a diet with defatted rice bran to double the fiber intake for 5 wk. Study 2 was a randomized, crossover, 10-wk feeding study performed in 14 volunteers who consumed a diet with rice bran oil (1/3 of the total dietary fat) substituted for an oil blend that had a fatty acid composition similar to that of the rice bran oil. Serum lipids and factor VII were measured in both studies. RESULTS: Defatted rice bran did not lower lipid concentrations. In study 2, total cholesterol was significantly lower with consumption of the diet containing rice bran oil than with consumption of the control diet. Moreover, with consumption of the rice bran oil diet, LDL cholesterol decreased by 7% (P < 0.0004), whereas HDL cholesterol was unchanged. CONCLUSIONS: Rice bran oil, not fiber, lowers cholesterol in healthy, moderately hypercholesterolemic adults. There were no substantial differences in the fatty acid composition of the diets; therefore, the reduction of cholesterol was due to other components present in the rice bran oil, such as unsaponifiable compounds.

Adult↗
PubMed2005

Individual variability in cardiovascular disease risk factor responses to low-fat and low-saturated-fat diets in men: body mass index, adiposity, and insulin resistance predict changes in LDL cholesterol.

BACKGROUND: Although reductions in total and saturated fat consumption are recommended to reduce the risk of cardiovascular disease, individual variability in plasma lipid responses exists. OBJECTIVE: Our aim was to determine the effect of adiposity and insulin resistance on the lipoprotein response to diets lower in total and saturated fat than the average American diet (AAD). DESIGN: A randomized, double-blind, 3-period crossover controlled feeding design was used to examine the effects on plasma lipids of 3 diets that differed in total fat: the AAD [designed to contain 38% fat and 14% saturated fatty acids (SFAs)], the Step I diet (30% fat with 9% SFAs), and the Step II diet (25% fat with 6% SFAs). The diets were fed for 6 wk each to 86 free-living, healthy men aged 22-64 y at levels designed to maintain weight. RESULTS: Compared with the AAD, the Step I and Step II diets lowered LDL cholesterol by 6.8% and 11.7%, lowered HDL cholesterol by 7.5% and 11.2%, and raised triacylglycerols by 14.3% and 16.2%, respectively. The Step II diet response showed significant positive correlations between changes in both LDL cholesterol and the ratio of total to HDL cholesterol and baseline percentage body fat, body mass index, and insulin. These associations were largely due to smaller reductions in LDL cholesterol with increasing percentage body fat, body mass index, or insulin concentrations. Subdivision of the study population showed that the participants in the upper one-half of fasting insulin concentrations averaged only 57% of the reduction in LDL cholesterol with the Step II diet of the participants in the lower half. CONCLUSION: Persons who are insulin resistant respond less favorably to Step II diets than do those who are insulin sensitive.

Adipose Tissue↗
PubMed2005

Daily intake of multivitamins during long-term intake of olestra in men prevents declines in serum vitamins A and E but not carotenoids.

The objective of this study was to determine whether vitamin supplementation during long-term (36 wk) ingestion of olestra supplemented with vitamin E could prevent decreases in vitamin E, vitamin A, and carotenoids. This was a 36-wk study of 37 healthy males randomly assigned to consume a control diet composed of 33% energy from fat, a similar diet in which one third of the energy from fat had been replaced with olestra, or a fat-reduced (25% of energy from fat) diet. Subjects also ingested a daily multivitamin (Centrum). Serum concentrations of alpha-tocopherol, retinol, beta-carotene, lycopene, and lutein + zeaxanthin were analyzed by HPLC. Subjects eating the olestra-containing diet had substantial decreases in serum beta-carotene, lycopene, and lutein + zeaxanthin, which occurred by 12 wk; these changes were found despite correcting for serum total cholesterol or BMI. Serum beta-carotene and lycopene concentrations were below the lower limit of the reference range (<0.186 and <0.298 mumol/L, respectively) at one or more time points. The slight decline in serum alpha-tocopherol concentration, significant at 24 wk, was caused by the decline in serum cholesterol. Retinol concentrations decreased with time in all 3 groups, but were not affected by olestra. We conclude that supplementation with a multivitamin containing vitamins A and E was adequate to prevent olestra-induced decrease in serum alpha-tocopherol and retinol. Olestra-induced decreases in serum beta-carotene, lycopene, and lutein + zeaxanthin were not prevented by the vitamin supplement used in this study.

Adult↗
PubMed2004

Estimated phytochemical content of the dietary approaches to stop hypertension (DASH) diet is higher than in the Control Study Diet.

The Dietary Approaches to Stop Hypertension (DASH) diet substantially lowers blood pressure and reduces blood lipid levels. The DASH diet menus were designed to reach beneficial levels of fiber, potassium, magnesium, and calcium, and therefore contain more fruits, vegetables, and whole grains relative to the control menus, and consequently more phytochemicals. Using the US Department of Agriculture food composition databases, the polyphenol, carotenoid, and phytosterol contents of the diets used in the DASH study were estimated. When compared with the control diet, the DASH diet is higher in flavonols, flavanones, flavan-3-ols, beta-carotene, beta-cryptoxanthin, lycopene, lutein+zeaxanthin, and phytosterols. Flavone levels are similar, whereas isoflavones are present in a small amount in the DASH diet. The roles of these compounds in disease risk reduction are becoming recognized. It therefore is possible that the health benefits of the DASH diet are partially attributable to the phytochemicals and might extend beyond cardiovascular disease risk reduction.

Blood Pressure↗
PubMed2003

Dietary quality assurance processes of the DASH-Sodium controlled diet study.

A thorough quality assurance (QA) program upholds the integrity of nutrition research studies by yielding reliable data and results. Continually evaluating the implementation of a procedure against a goal and making adjustments when needed enhance the quality of a study's conduct and outcomes. Controlled diet studies require QA processes at various steps beginning with the screening of study participants, through diet preparation and delivery to data collection. Staff training and observations with monitoring activities, are important so tasks are completed according to protocol. When several clinical sites participate as partners in a controlled diet study, uniform procedures must be followed and a formal standardized QA program will assist. The Dietary Approaches to Stop Hypertension (DASH)-Sodium study employed such a program, described in this article, that included training staff, observing procedures, monitoring data for completeness and accuracy, evaluating processes, giving feedback, and documenting that tasks were done according to protocol. Furthermore, QA processes were used in the areas of participant screening, orientation, diet adherence, food procurement and preparation, and exit interviews. Other researchers may implement similar activities to ensure quality in their nutrition research programs.

Cohort Studies↗
PubMed2003

An overview of methodologies, proficiencies, and training resources for controlled feeding studies.

Dietary intervention studies of human beings produce valuable information regarding dietary effects on biological processes and risk factors for chronic diseases. Using the well-controlled feeding approach, participants consume only foods that have been precisely prepared in a research kitchen, whereas in behavioral counseling studies, participants self-select their foods within guidelines. Because controlled feeding studies meticulously control experimental diets, they are intellectually and logistically challenging to conduct. They afford exciting opportunities for dietetic professionals in designing protocols, developing budgets, and collaborating in multidisciplinary research teams. Research dietitians use food composition data and chemical analysis of menus to prepare research diets with precision. They determine the energy requirements of subjects and adjust diets as required, most often for weight maintenance, throughout the study. All people involved in research must be attentive to the ethical treatment of the study participants while motivating them to adhere to the protocol requirements. Dietitians possess many of these skills, but may require training specific to well-controlled feeding studies. Information related to the conduct of controlled feeding studies has recently become more accessible. We provide an overview of well-controlled feeding study methodologies, proficiencies for planning and implementing these studies, and training resources.

Diet↗
PubMed2002

Effect on body weight of replacing dietary fat with olestra for two or ten weeks in healthy men and women.

OBJECTIVE: To examine in two separate studies the effects of replacing dietary fat with Olestra on body composition and weight change in healthy young men and women. METHODS: Ten healthy, lean young men participated in Study One that was a 22-day single blind, within-subject design. After a control diet (40% fat) for eight days Study One subjects received an Olestra-substituted diet (31% metabolizable fat) for 14 days. Study Two was a randomized parallel-arm clinical trial with 15 healthy, lean and overweight young women. These subjects were randomly assigned to receive a control diet (40% fat), an Olestra-containing diet (31% metabolizable fat) or a reduced-fat diet (31% fat) for 10 weeks. All foods were provided to the subjects, and energy intakes were not restricted. The primary endpoint in both studies was change from baseline in body weight. In Study Two, body composition was measured by dual energy x-ray absorptiometry. In both studies, food intake and nutrient compensation were assessed. RESULTS: In Study One fat substitution by Olestra resulted in a significant 1.7 kg weight loss from baseline. In Study Two, change in body weight and body fat from baseline were statistically significant in all groups, but the group with Olestra lost significantly more weight from baseline (-5.0 kg) than the other two groups. In Study One there was partial compensation for the decreased energy intake, while in Study Two, compensation was seen only for those on the reduced-fat diet. CONCLUSION: Replacement of 1/3 of dietary fat with Olestra in periods of up to 10 weeks results in weight loss in men and women.

Absorptiometry, Photon↗
PubMed2002

Effect of diets enriched in almonds on insulin action and serum lipids in adults with normal glucose tolerance or type 2 diabetes.

BACKGROUND: Nuts appear to have cardiovascular benefits but their effect in diabetic patients is unclear. OBJECTIVE: The objective was to assess effects of almond-enriched diets on insulin sensitivity and lipids in patients with normoglycemia or type 2 diabetes. DESIGN: Study 1 assessed the effect of almonds on insulin sensitivity in 20 free-living healthy volunteers who received 100 g almonds/d for 4 wk. Study 2 was a randomized crossover study that compared 4 diets in 30 volunteers with type 2 diabetes: 1) high-fat, high-almond (HFA; 37% total fat, 10% from almonds); 2) low-fat, high-almond (LFA; 25% total fat, 10% from almonds); 3) high-fat control (HFC; 37% total fat, 10% from olive or canola oil); and 4) low-fat control (LFC; 25% total fat, 10% from olive or canola oil). After each 4-wk diet, serum lipids and oral glucose tolerance were measured. RESULTS: In study 1, almond consumption did not change insulin sensitivity significantly, although body weight increased and total and LDL cholesterol decreased by 21% and 29%, respectively (P < 0.05). In study 2, total cholesterol was lowest with the HFA diet (4.46 +/- 0.14, 4.52 +/- 0.14, 4.63 +/- 0.14, and 4.63 +/- 0.14 mmol/L with the HFA, HFC, LFA, and LFC diets, respectively; P = 0.0004 for fat level). HDL cholesterol was significantly lower with the almond diets (P = 0.002); however, no significant effect of fat source on LDL:HDL was observed. Glycemia was unaffected. CONCLUSIONS: Almond-enriched diets do not alter insulin sensitivity in healthy adults or glycemia in patients with diabetes. Almonds had beneficial effects on serum lipids in healthy adults and produced changes similar to high monounsaturated fat oils in diabetic patients.

Adult↗
PubMed2002

Effects of diets enriched in saturated (palmitic), monounsaturated (oleic), or trans (elaidic) fatty acids on insulin sensitivity and substrate oxidation in healthy adults.

OBJECTIVE: Diets high in total and saturated fat are associated with insulin resistance. This study examined the effects of feeding monounsaturated, saturated, and trans fatty acids on insulin action in healthy adults. RESEARCH DESIGN AND METHODS: A randomized, double-blind, crossover study was conducted comparing three controlled 4-week diets (57% carbohydrate, 28% fat, and 15% protein) enriched with different fatty acids in 25 healthy men and women. The monounsaturated fat diet (M) had 9% of energy as C18:1cis (oleic acid). The saturated fat diet (S) had 9% of energy as palmitic acid, and the trans fatty acid diet (T) had 9% as C18:1trans. Body weight was kept constant throughout the study. After each diet period, insulin pulsatile secretion, insulin sensitivity index (S(I)) by the minimal model method, serum lipids, and fat oxidation by indirect calorimetry were measured. RESULTS: Mean S(I) for the M, S, and T diets was 3.44 +/- 0.26, 3.20 +/- 0.26, and 3.40 +/- 0.26 x 10(-4) min(-1). microU(-1). ml(-1), respectively (NS). S(I) decreased by 24% on the S versus M diet in overweight subjects but was unchanged in lean subjects (NS). Insulin secretion was unaffected by diet, whereas total and HDL cholesterol increased significantly on the S diet. Subjects oxidized the least fat on the M diet (26.0 +/- 1.5 g/day) and the most fat on the T diet (31.4 +/- 1.5 g/day) (P = 0.02). CONCLUSIONS: Dietary fatty acid composition significantly influenced fat oxidation but did not impact insulin sensitivity or secretion in lean individuals. Overweight individuals were more susceptible to developing insulin resistance on high-saturated fat diets.

Adult↗
PubMed2002

Changes in food intake and body weight associated with basic combat training.

This research project evaluated changes in food selections, food intake, and body weight during 8 weeks of basic combat training (BCT). During the first week of BCT, 139 soldiers from two companies volunteered for participation in the study. In the eighth week of BCT, 92 soldiers were available for retesting. A digital photography method for measuring food selections and food intake was developed for this study. Fruit intake of soldiers was very low at the beginning and end of BCT. Food intake for grains and milk products was low during the first week of BCT but improved by the end of BCT. Average body weight decreased during the 8 weeks of BCT, but heavier soldiers tended to lose weight and thinner soldiers tended to gain weight. These findings suggest that the overall effect of BCT was a trend toward improvement of healthy eating and healthy body weight.

Adult↗