Alternatives for macronutrient intake and chronic disease: a comparison of the OmniHeart diets with popular diets and with dietary recommendations

BACKGROUND: Enhancements to current dietary advice to prevent chronic disease are of great clinical and public health importance. The OmniHeart Trial compared 3 diets designed to reduce cardiovascular disease (CVD) risk-one high in carbohydrate and 2 that replaced carbohydrate with either unsaturated fat or protein. The lower carbohydrate diets improved the CVD risk factors. Several popular diets claiming health benefits emphasize carbohydrate, fat, or protein or various combined approaches. OBJECTIVE: The objective of this study was to compare the macronutrient contents of the OmniHeart trial diets to those of several popular diets and to evaluate each diet for consistency with national health guidelines. DESIGN: The macronutrient contents of 7-d menu plans from the OmniHeart Study, Dietary Approaches to Stop Hypertension (DASH), Zone, Atkins, Mediterranean, South Beach, and Ornish diets were evaluated for consistency with the US Food and Nutrition Board's Acceptable Macronutrient Distribution Ranges (AMDRs) and with the dietary recommendations of several health organizations. RESULTS: The OmniHeart diets fulfilled the major AMDRs, but, of the popular diets, only the Zone diet did. The OmniHeart diets were generally consistent with national guidelines to prevent cancer, diabetes, and heart disease, whereas most popular diets had limitations for fulfilling one or more guidelines. CONCLUSIONS: Although the OmniHeart protein and unsaturated fat diets were superior to the carbohydrate diet in improving CVD risk, all 3 study diets were consistent with national guidelines to reduce chronic disease risk, which suggests that the guidelines might now be fine-tuned to optimize disease prevention. Popular diets vary in their nutritional adequacy and consistency with guidelines for risk reduction.     

Low-carbohydrate diets, dietary approaches to stop hypertension-style diets, and the risk of postmenopausal breast cancer

The authors prospectively examined the association between the Dietary Approaches to Stop Hypertension diet score, overall, animal-based, and vegetable-based low-carbohydrate-diet scores, and major plant food groups and the risk of postmenopausal breast cancer in 86,621 women in the Nurses' Health Study. Diet scores were calculated by using data from up to 7 food frequency questionnaires, with follow-up from 1980 to 2006. The authors ascertained 5,522 incident cases of breast cancer, including 3,314 estrogen receptor-positive (ER+) cancers and 826 estrogen receptor-negative (ER-) cancers. After adjustment for potential confounders, the Dietary Approaches to Stop Hypertension diet score was associated with a lower risk of ER- cancer (relative risk comparing extreme quintiles = 0.80, 95% confidence interval: 0.64, 1.01; P trend = 0.02). However, this was largely explained by higher intakes of fruits and vegetables. The authors also observed an inverse association between risk of ER- cancer and the vegetable-based, low-carbohydrate-diet score (corresponding relative risk = 0.81, 95% confidence interval: 0.65, 1.01; P trend = 0.03). High total fruit and low-protein vegetable intakes were associated with a lower risk of ER- cancer (relative risk comparing extreme quintiles = 0.71, 95% confidence interval: 0.55, 0.90; P trend = 0.005). No association was found between ER+ tumors and fruit and vegetable intakes. A diet high in fruits and vegetables, such as one represented by the Dietary Approaches to Stop Hypertension diet score, was associated with a lower risk of ER- breast cancer. In addition, a diet high in plant protein and fat and moderate in carbohydrate content was associated with a lower risk of ER- cancer.     

Effect of protein, unsaturated fat, and carbohydrate intakes on plasma apolipoprotein B and VLDL and LDL containing apolipoprotein C-III: results from the OmniHeart Trial

BACKGROUND: Plasma apolipoprotein B (apo B) and VLDL and LDL with apolipoprotein C-III (apo C-III) are independent risk factors for cardiovascular disease (CVD). Dietary intake affects lipoprotein concentration and composition related to those apolipoproteins. OBJECTIVE: We studied differences in apo B lipoproteins with and without apo C-III after 3 healthy diets based on the Dietary Approaches to Stop Hypertension Trial diet. DESIGN: Healthy participants (n = 162) were fed each of 3 healthy diets for 6 wk in a crossover design. Diets differed by emphasis of either carbohydrate (Carb), unsaturated fat (Unsat), or protein (Prot). Blood was collected at baseline and after diets for analysis. RESULTS: Compared with the Carb diet, the Prot diet reduced plasma apo B and triglycerides in VLDL with apo C-III (16%, P = 0.07; 11%, P = 0.05, respectively) and apo B in LDL with apo C-III (16%, P = 0.04). Compared with the Unsat diet, the Prot diet reduced triglycerides in VLDL with apo C-III (16%, P = 0.02). Compared with baseline (subjects' usual diet was higher in saturated fat), the Prot diet reduced apo B in LDL with apo C-III (11%, P = 0.05), and all 3 diets reduced plasma total apo B (6-10%, P < 0.05) and apo B in the major type of LDL, LDL without apo C-III (8-10%, P < 0.01). All 3 diets reduced the ratio of apo C-III to apo E in VLDL. CONCLUSIONS: Substituting protein for carbohydrate in the context of a healthy dietary pattern reduced atherogenic apo C-III-containing LDL and its precursor, apo C-III-containing VLDL, resulting in the most favorable profile of apo B lipoproteins. In addition, compared with a typical high-saturated fat diet, healthy diets that emphasize carbohydrate, protein, or unsaturated fat reduce plasma total and LDL apo B and produce a lower more metabolically favorable ratio of apo C-III to apo E.     

Dietary Approaches to Stop Hypertension (DASH) diet: applicability and acceptability to a UK population

Background:  The Dietary Approaches to Stop Hypertension (DASH) diet is widely promoted in the USA for the prevention and treatment of high blood pressure. It is high in fruit and vegetables, low-fat dairy and wholegrain foods and low in saturated fat and refined sugar. To our knowledge, the use of this dietary pattern has not been assessed in a free-living UK population.
Methods:  The DASH diet was adapted to fit UK food preferences and portion sizes. Fourteen healthy subjects followed the adapted DASH diet for 30 days in which they self-selected all food and beverages. Dietary intake was assessed by 5-day food diaries completed before and towards the end of the study. Blood pressure was measured at the beginning and end of the study to assess compliance to the DASH style diet.
Results:  The DASH diet was easily adapted to fit with UK food preferences. Furthermore, it was well tolerated and accepted by subjects. When on the DASH style diet, subjects reported consuming significantly ( P  <   0.01) more carbohydrate and protein and less total fat (5%, 6% and 9% total energy, respectively). Sodium intakes decreased by 860 mg day⁻¹ ( P  <   0.001). Systolic and diastolic blood pressure decreased significantly ( P  <   0.05) by 4.6 and 3.9 mmHg, respectively when on the DASH style diet.
Conclusions:  The DASH style diet was well accepted and was associated with a decrease in blood pressure in normotensive individuals and should be considered when giving dietary advice to people with elevated blood pressure in the UK.     

Clinical inquiries: What is the dietary treatment for low HDL cholesterol?

Low-carbohydrate diets raise high-density lipoprotein (HDL) cholesterol levels by approximately 10%; soy protein with isoflavones raises HDL by 3% (strength of recommendation [SOR]: C, based on meta-analysis of physiologic parameters). The Dietary Approaches to Stop Hypertension (DASH) diet and multivitamin supplementation raise HDL 21% to 33% (SOR: C, based on single randomized trial each measuring physiologic parameters). No other dietary interventions studied raise HDL (SOR: C, based on meta-analysis of physiologic parameters).     

The DASH diet may have beneficial effects on bone health

Recent data from an ancillary study to the Dietary Approaches to Stop Hypertension (DASH)-Sodium trial suggest that while sodium intake had very little effect on bone metabolism, the DASH diet (over 30 days) significantly reduced markers of bone turnover. This DASH diet-induced reduction in bone turnover, if sustained, may improve bone mineral status.     

Effect of high-carbohydrate or high-cis-monounsaturated fat diets on blood pressure: a meta-analysis of intervention trials

BACKGROUND: The Dietary Approaches to Stop Hypertension (DASH) diet is recommended to manage blood pressure. The DASH diet is low in saturated fat, but it is not clear whether saturated fat should be preferentially replaced with carbohydrate or unsaturated fat, especially cis-monounsaturated fat. OBJECTIVE: A meta-analysis of intervention studies comparing high-carbohydrate and high-cis-monounsaturated fat diets was conducted to increase understanding of the effect of carbohydrate and cis-monounsaturated fat on blood pressure. DESIGN: For study diets to be included in the analysis, they had to be isoenergetic, and the subjects' body weight had to remain stable. Ten studies (6 randomized crossover, 1 randomized parallel, and 3 nonrandomized) met the inclusion criteria. RESULTS: According to the random-effects model, which incorporates between-study variation to estimate the overall effect, diets rich in carbohydrate resulted in significantly higher systolic blood pressure [x(-) difference: 2.6 (95% CI: 0.4, 4.7) mm Hg; P=0.02] and diastolic blood pressure [1.8 (0.01, 3.6) mm Hg; P=0.05] than did diets rich in cis-monounsaturated fat. When the meta-analysis was limited to randomized crossover studies, both systolic [1.3 (-0.3, 2.9) mm Hg; P=0.11] and diastolic [0.9 (-0.2, 2.1) mm Hg; P=0.11] blood pressure were higher with a high-carbohydrate than with a high cis-monounsaturated fat diet, but the differences were not significant. CONCLUSIONS: Diets rich in carbohydrate may be associated with slightly higher blood pressure than diets rich in cis-monounsaturated fat. However, the magnitude of the difference may not justify making recommendations to alter the carbohydrate and cis-monounsaturated fat content of the diet to manage blood pressure.     

Physical Fitness but Not Diet Quality Distinguishes Lean and Normal Weight Obese Adults

BackgroundIndividuals with normal weight obesity (NWO) have increased cardiometabolic disease and mortality risk, but factors contributing to NWO development are unknown.ObjectiveThe objective of this study was to determine whether diet quality scores and physical fitness levels differed between adults classified as lean, NWO, and overweight-obese. Secondary objectives of the study were to compare clinical biomarkers and food groups and macronutrient intakes between the three groups, and to test for associations between body composition components with diet quality scores and physical fitness levels.DesignThis is a secondary data analysis from a cross-sectional study that included metropolitan university and health care system employees. Body composition was measured by dual energy x-ray absorptiometry. Individuals with a body mass index <25 kg/m² and body fat >23% for men and >30% for women were classified as having NWO. Alternate Healthy Eating Index, Dietary Approaches to Stop Hypertension score, and Mediterranean Diet Score were calculated from Block food frequency questionnaires. Physical fitness was assessed by measuring maximal oxygen uptake (VO₂ maximum) during treadmill testing.Participants/settingThis study included 693 adults (65% women, mean age 48.9 ± 11.5 years) enrolled between 2007 and 2013 in Atlanta, GA.Main outcome measuresThe main outcome measures were Alternate Healthy Eating Index, Dietary Approaches to Stop Hypertension, and Mediterranean Diet Score diet quality scores and maximal oxygen uptake.Statistical analysesMultiple linear regression analyses with post hoc comparisons were used to investigate group differences in fitness, diet quality, and biomarkers. Regression analyses were also used to examine relationships between diet quality scores and fitness with body composition.ResultsVO₂ maximum was significantly lower in the NWO compared with the lean group (36.2 ± 0.8 mL/min/kg vs 40.2 ± 1.0 mL/min/kg; P < 0.05). Individuals with NWO reported similar diet quality to lean individuals and more favorable Alternate Healthy Eating Index and Dietary Approaches to Stop Hypertension scores than individuals with overweight-obesity (P < 0.05). Diet quality scores and physical fitness levels were inversely associated with percent body fat and visceral adipose tissue (P < 0.05), regardless of weight status. Individuals with NWO exhibited higher fasting blood insulin concentrations, insulin resistance, low-density lipoprotein cholesterol, and triglyceride levels, and significantly lower high-density lipoprotein cholesterol levels than lean individuals (P < 0.05).ConclusionsPhysical fitness was significantly decreased in individuals with NWO compared with lean individuals. Higher diet quality was associated with decreased total and visceral fat but did not distinguish individuals with NWO from lean individuals.     

Self-selected macronutrient diet affects energy and glucose metabolism in brown fat-ablated mice

OBJECTIVE: Obese transgenic UCP-DTA mice have largely ablated brown adipose tissue and develop obesity and diabetes, which are highly susceptible to a high-fat diet. We investigated macronutrient self-selection and its effect on development of obesity, diabetes, and energy homeostasis in UCP-DTA mice. RESEARCH METHODS AND PROCEDURES: UCP-DTA and wild-type littermates were fed a semisynthetic macronutrient choice diet (CD) ad libitum from weaning until 17 weeks. Energy homeostasis was assessed by measurement of food intake, food digestibility, body composition, and energy expenditure. Diabetes was assessed by blood glucose measurements and insulin tolerance test. RESULTS: Wild-type and UCP-DTA mice showed a high fat preference and increased energy digestion on CD compared with a low-fat standard diet. On CD, wild-type mice accumulated less body fat (16.9%) than UCP-DTA (32.6%) mice, although they had a higher overall energy intake. Compared with wild-type mice, resting metabolic rate was reduced in UCP-DTA mice irrespective of diet. UCP-DTA mice progressively decreased their carbohydrate intake, resulting in an almost complete avoidance of carbohydrate. UCP-DTA mice developed severe insulin resistance but showed decreased fed and fasted blood glucose on CD. DISCUSSION: In contrast to wild-type mice, UCP-DTA mice were not able to reduce their weight gain efficiency on CD. This suggests that, because of the high fat preference of the background strain and the increased metabolic efficiency, brown adipose tissue-deficient mice still develop obesity and insulin resistance on a macronutrient CD even when decreasing overall energy intake. Through the avoidance of carbohydrates, however, they are able to maintain normoglycemia.     

Phytosterol-Deficient and High-Phytosterol Diets Developed for Controlled Feeding Studies

Phytosterols reduce cholesterol absorption and low-density lipoprotein cholesterol concentrations, but the quantity and physiological significance of phytosterols in common diets are generally unknown because nutrient databases do not contain comprehensive phytosterol data. The primary aim of this study was to design prototype phytosterol-deficient and high-phytosterol diets for use in controlled feeding studies of the influence of phytosterols on health. A second aim was to quantify the phytosterol content of these prototype diets and three other diets consumed in the United States. This study was conducted from June 2001 to September 2008 and involved designing, preparing, and then analyzing five different diets: an experimental phytosterol-deficient control diet, a relatively high-phytosterol diet based on the Dietary Approaches to Stop Hypertension diet, American Heart Association diet, Atkins lifetime maintenance plan, and a vegan diet. A single day of meals for each diet was homogenized and the resulting composites were analyzed for free, esterified, and glycosylated phytosterols by gas chromatography. Independent samples t tests were used to compare the diets' total phytosterol content. The total phytosterol content of the experimental phytosterol-deficient diet was 64 mg/2,000 kcal, with progressively larger quantities in Atkins, American Heart Association, vegan, and the high-phytosterol Dietary Approaches to Stop Hypertension diet (163, 340, 445, and 500 mg/2,000 kcal, respectively). Glycosylated phytosterols, which are often excluded from phytosterol analyses, comprised 15.9%±5.9% of total phytosterols. In summary, phytosterol-deficient and high-phytosterol diets that conform to recommended macronutrient guidelines and are palatable can now be used in controlled feeding studies.     

Adherence to the Dietary Approaches to Stop Hypertension (DASH) and risk of Nonalcoholic Fatty Liver Disease

This case–control study was conducted to examine the association between adherence to the Dietary Approaches to Stop Hypertension (DASH) diet and risk of Nonalcoholic Fatty Liver Disease (NAFLD) development in 102 patients with newly diagnosed NAFLD and 204 controls. Adherence to DASH-style diet was assessed using a validated food frequency questionnaire, and a DASH diet score based on food and nutrients emphasized or minimized in the DASH diet. Participants in the top quartile of DASH diet score were 30% less likely to have NAFLD (OR: 0.0.70; 95%?CI: 0.61, 0.80); however, more adjustment for dyslipidemia and body mass index changed the association to non-significant (OR: 0.92; 95%?CI: 0.73, 1.12). In conclusion, we found an inverse relationship between the DASH-style diet and risk of NAFLD. Prospective studies are needed to confirm this association.     

Effects on blood lipids of a blood pressure-lowering diet: the Dietary Approaches to Stop Hypertension (DASH) Trial.

BACKGROUND: Effects of diet on blood lipids are best known in white men, and effects of type of carbohydrate on triacylglycerol concentrations are not well defined. OBJECTIVE: Our goal was to determine the effects of diet on plasma lipids, focusing on subgroups by sex, race, and baseline lipid concentrations. DESIGN: This was a randomized controlled outpatient feeding trial conducted in 4 field centers. The subjects were 436 participants of the Dietary Approaches to Stop Hypertension (DASH) Trial [mean age: 44.6 y; 60% African American; baseline total cholesterol: < or = 6.7 mmol/L (< or = 260 mg/dL)]. The intervention consisted of 8 wk of a control diet, a diet increased in fruit and vegetables, or a diet increased in fruit, vegetables, and low-fat dairy products and reduced in saturated fat, total fat, and cholesterol (DASH diet), during which time subjects remained weight stable. The main outcome measures were fasting total cholesterol, LDL cholesterol, HDL cholesterol, and triacylglycerol. RESULTS: Relative to the control diet, the DASH diet resulted in lower total (-0.35 mmol/L, or -13.7 mg/dL), LDL- (-0.28 mmol/L, or -10.7 mg/dL), and HDL- (-0.09 mmol/L, or -3.7 mg/dL) cholesterol concentrations (all P < 0.0001), without significant effects on triacylglycerol. The net reductions in total and LDL cholesterol in men were greater than those in women by 0.27 mmol/L, or 10.3 mg/dL (P = 0.052), and by 0.29 mmol/L, or 11.2 mg/dL (P < 0.02), respectively. Changes in lipids did not differ significantly by race or baseline lipid concentrations, except for HDL, which decreased more in participants with higher baseline HDL-cholesterol concentrations than in those with lower baseline HDL-cholesterol concentrations. The fruit and vegetable diet produced few significant lipid changes. CONCLUSIONS: The DASH diet is likely to reduce coronary heart disease risk. The possible opposing effect on coronary heart disease risk of HDL reduction needs further study.     

A comparison of food-based recommendations and nutrient values of three food guides: USDA's MyPyramid, NHLBI's Dietary Approaches to Stop Hypertension Eating Plan, and Harvard's Healthy Eating Pyramid

The purpose of this research was to compare food-based recommendations and nutrient values of three food guides: the US Department of Agriculture's MyPyramid; the National Heart, Lung, and Blood Institute's Dietary Approaches to Stop Hypertension Eating Plan, and Harvard University's Healthy Eating Pyramid. Estimates of nutrient values associated with following each of the food guides at the 2,000-calorie level were made using a composite approach. This approach calculates population-weighted nutrient composites for each food group and subgroup, assuming average choices within food groups. Nutrient estimates were compared to the Dietary Reference Intakes and other goals and limits. Recommendations were similar regarding almost all food groups for both the type and amount of foods. Primary differences were seen in the types of vegetables and protein sources recommended and the amount of dairy products and total oil recommended. Overall nutrient values were also similar for most nutrients, except vitamin A, vitamin E, and calcium. These food guides were derived from different types of nutrition research, yet they share consistent messages: eat more fruits, vegetables, legumes, and whole grains; eat less added sugar and saturated fat; and emphasize plant oils.     

High-density lipoprotein-cholesterol and diet in a healthy elderly population.

This study examined how high-density lipoprotein-cholesterol (HDL-C) correlated with a 3-day food record of fat, protein, carbohydrate, and alcohol consumption in a group of 270 healthy subjects over age 60. HDL-C concentrations correlated with alcohol consumption (expressed as grams/day) (r = + .25, P less than .001), and inversely with total carbohydrate (r = - .18, P less than .01) and refined carbohydrate (r = - .17, P less than .01) ingestion (expressed as a percent of total caloric intake). Subjects consuming diets low in either total carbohydrate or refined carbohydrate had 10 to 20% higher HDL-C levels than did those consuming diets high in these food substances. The relationships between HDL-C levels and alcohol and carbohydrate ingestion were independent of other variables which correlated with HDL-C levels. Dietary fat (total fat, saturated fat, unsaturated fat, and cholesterol) did not correlate with HDL-C. LDL-cholesterol and triglyceride levels did not correlate with any dietary variable measured.     

Acceptability of sodium-reduced research diets, including the Dietary Approaches To Stop Hypertension diet, among adults with prehypertension and stage 1 hypertension

OBJECTIVE: Examine the acceptability of sodium-reduced research diets. DESIGN: Randomized crossover trial of three sodium levels for 30 days each among participants randomly assigned to one of two dietary patterns. PARTICIPANTS/SETTING: Three hundred fifty-four adults with prehypertension or stage 1 hypertension who were participants in the Dietary Approaches to Stop Hypertension (DASH-Sodium) outpatient feeding trial. INTERVENTION: Participants received their assigned diet (control or DASH, rich in fruits, vegetables, and low-fat dairy products), each at three levels of sodium (higher, intermediate, and lower) corresponding to 3,500, 2,300, and 1,200 mg/day (150, 100, and 50 mmol/day) per 2,100 kcal. MAIN OUTCOME MEASURES: Nine-item questionnaire on liking and willingness to continue the assigned diet and its level of saltiness using a nine-point scale, ranging from one to nine. STATISTICAL ANALYSES PERFORMED: Generalized estimating equations to test participant ratings as a function of sodium level and diet while adjusting for site, feeding cohort, carryover effects, and ratings during run-in. RESULTS: Overall, participants rated the saltiness of the intermediate level sodium as most acceptable (DASH group: 5.5 for intermediate vs 4.5 and 4.4 for higher and lower sodium; control group: 5.7 for intermediate vs 4.9 and 4.7 for higher and lower sodium) and rated liking and willing to continue the DASH diet more than the control diet by about one point (ratings range from 5.6 to 6.6 for DASH diet and 5.2 to 6.1 for control diet). Small race differences were observed in sodium and diet acceptability. CONCLUSIONS: Both the intermediate and lower sodium levels of each diet are at least as acceptable as the higher sodium level in persons with or at risk for hypertension.     

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.     

Association of energy intake and macronutrient composition with overweight and obesity in malay women from klang valley

This cross-sectional study investigates the association between energy intake and macronutrient composition of the diet with overweight and obesity among Malaysian women. One hundred and fifteen adult Malay women aged 20 to 59 years (mean age 37.2±7.6 years) were interviewed. Dietary intake was assessed using the food history method. Body weight status was assessed using weight, height, waist circumference and fat percentage measurements. When energy intake was assessed for accuracy, only 41% of the subjects (n=47) were normal energy reporters. Among the normal energy reporters, 55% were of normal weight whereas 32% and 13% were overweight and obese. Mean energy intake for normal weight, overweight and obese subjects was 1685±199 kcal/day, 1810±166 kcal/day and 2119±222 kcal/day, respectively. Energy intake increased with body mass index (BMI) category. Among the overweight and obese, energy intake was respectively higher by 125 kcal/day and 434 kcal/day as compared to their normal weight counterparts (p< 0.001). There was also a significant, moderate and positive correlation between energy intake and BMI (r=0.635), waist circumference (r=0.545), and body fat percentage (r=0.534). When macronutrient composition of diet was analysed (% energy and g/1000 kcal), there was no significant difference in carbohydrate, protein or fat intake between the obese, overweight and normal weight subjects. There was also no significant correlation between macronutrient composition of the diet and body weight status. Based on these findings, we conclude that the subjects' body weight status is likely to be influenced by energy intake rather than the macronutrient composition of the diet.     

Satiety related to 24 h diet-induced thermogenesis during high protein/carbohydrate vs high fat diets measured in a respiration chamber.

OBJECTIVE: Assessment of a possible relationship between perception of satiety and diet-induced thermogenesis, with different macronutrient compositions, in a controlled situation over 24 h. DESIGN: Two diets with different macronutrient compositions were offered to all subjects in randomized order. SETTING: The study was executed in the respiration chambers at the department of Human Biology, Maastricht University. SUBJECTS: Subjects were eight females, ages 23-33 y, BMI 23+/-3 kg/m2, recruited from University staff and students. INTERVENTIONS: Subjects were fed in energy balance, with protein/carbohydrate/fat: 29/61/10 and 9/30/61 percentage of energy, with fixed meal sizes and meal intervals, and a fixed activity protocol, during 36 h experiments in a respiration chamber. The appetite profile was assessed by questionnaires during the day and during meals. Diet induced thermogenesis was determined as part of the energy expenditure. RESULTS: Energy balance was almost complete, with non-significant deviations. Diet-Induced-Thermogenesis (DIT) was 14.6+/-2.9%, on the high protein/carbohydrate diet, and 10.5+/-3.8% on the high fat diet (P < 0.01). With the high protein/high carbohydrate diet, satiety was higher during meals (P < 0.001; P < 0.05), as well as over 24 h (P < 0.001), than with the high fat diet. Within one diet, 24 h DIT and satiety were correlated (r = 0.6; P < 0.05). The difference in DIT between the diets correlated with the differences in satiety (r = 0.8; P < 0.01). CONCLUSION: In lean women, satiety and DIT were synchronously higher with a high protein/high carbohydrate diet than with a high fat diet. Differences (due to the different macronutrient compositions) in DIT correlated with differences in satiety over 24 h.     

Estimation of energy requirements in a controlled feeding trial

BACKGROUND: Estimating energy requirements is a frequent task in clinical studies. OBJECTIVE: We examined weight patterns of participants enrolled in a clinical trial and evaluated factors that may affect weight stabilization. The Harris-Benedict equation and the FAO/WHO equation, used in conjunction with physical activity levels estimated with the 7-d Physical Activity Recall, were compared for estimating energy expenditure. DESIGN: This was a multicenter, randomized controlled feeding trial with participants of the Dietary Approaches to Stop Hypertension Trial. For 11 wk, the amount of food participants received was adjusted to maintain their body weights as close to their initial weights as possible. Change-point regression techniques were used to identify weight-stable periods. Factors related to achieving weight stabilization were examined with logistic regression. RESULTS: A stable weight was achieved by 86% of the 448 participants during the run-in period and by 78% during the intervention period. Energy intake averaged 11 +/- 2.4 MJ/d (2628 +/- 578 kcal/d), with most participants (n = 270) requiring 9-13 MJ/d (2100-3100 kcal/d). The difference between predicted and observed intakes was highest at high estimated energy intakes, mainly because of high and probably incorrect estimates of the activity factor. Participants with lower energy intakes tended to need less adjustment of their energy intakes to maintain a stable weight than did participants with higher energy intakes. CONCLUSIONS: Weight stabilization is not affected by diet composition, sex, race, age, or baseline weight. Either the Harris-Benedict equation or the FAO/WHO equation can be used to estimate energy needs. Activity factors > 1.7 often lead to overestimation of energy needs.     

Selection of carbohydrate to protein ratio and correlations with weight gain and body fat in rats allowed three dietary choices

In order to determine the spontaneous macronutrient choice of a normal rat population, we allowed growing animals to choose their food among three isocaloric diets: 5% protein - 40% carbohydrate; 45% protein - 40% carbohydrate and 5% protein - 70% carbohydrate, and we measured macronutrient intake, carbohydrate to protein (C/P) ratio and weight gain twice weekly during 9 weeks. At the end of the study, final body weight gain and fat accretion as well as brain serotonin content were measured. Protein consumption increased and fat intake decreased steadily during the assay (from 18.8 to 29 kcal% vs. 35.7 to 25.2 kcal%) whereas carbohydrate consumption remained constant (approx. 46 kcal%) ("carbohydrate homeostasis"), and as a consequence the C/P ratio dropped. There were great variations in total protein consumption between animals (13-32 kcal%) and an inverse relationship with fat intake because carbohydrate consumption was constant. Daily weight gain was negatively correlated with the corresponding C/P ratio, as were final weight gain and body fat content with the global C/P ratio characterizing the food choice of each rat. The concentrations of brain serotonin and 5-hydroxyindole acetic acid were rather uniform and did not show any correlations with any of the other variables. The percent food protein chosen by the animal determined the outcome of the trial at 9 weeks, i.e. food intake, weight gain and body fat accretion. In this experimental model, body fat accumulation is, therefore, directly linked to the protein content of the diet, inversely proportional to the fat level and not related to the carbohydrate content. Since the animals increase the proportion of protein in their food with age above basic nutritional requirements, it is postulated that the macronutrient choice of the rat is also determined by the need of the brain for a proper and balanced supply of neurotransmitter precursors adapted to the situation of each animal.