Dietary fat consumption and health.

Dietary Guidelines have emerged over the past 30 years recommending that Americans limit their consumption of total fat and saturated fat as one way to reduce the risk of a range of chronic diseases. However, a low-fat diet is not a no-fat diet. Dietary fat clearly serves a number of essential functions. For example, maternal energy deficiency, possible exacerbated by very low-fat intakes (< 15% of energy), is one key determinant in the etiology of low birth weight. The debate continues over recommendations for limiting total fat and saturated fatty acid intake in children. Recent evidence indicates that diets with adequate energy providing less than 30% of energy from fat are sufficient to promote normal growth and normal sexual maturation. More attention needs to be devoted to the effect of dietary fat reduction on the nutrient density of children's diets. The association between dietary fat and CHD has been extensively studied. Diets high in saturated fatty acids and trans fatty acids increase LDL cholesterol levels, and in turn, the risk of heart disease. The relationship between high-carbohydrate/low-fat diets and CHD is more ambiguous because high-carbohydrate diets induce dyslipidemia in certain individuals. Obesity among adults and children is now of epidemic proportions in the United States. High-fat diets leading to excessive energy intakes are strongly linked to the increasing obesity in the United States. However, the prevalence of obesity has increased during the same time period that dietary fat intake (both in absolute terms and as a percentage of total dietary energy) has decreased. These trends suggest that a concomitant decrease in total dietary energy and modifications of other lifestyle factors, such as physical activity, also need to be emphasized. Obesity is also an independent risk factor for the development of diabetes. The current availability of fat-modified foods offers the potential for dietary fat reduction and treatment of the comorbidities associated with diabetes. However, to date, few studies have documented the effectiveness of fat-modified foods as part of a weight loss regimen or in reduction in CHD risks among individuals with diabetes mellitus. The association between total dietary fat and cancer is still under debate. While there is some evidence demonstrating associations between dietary fat intake and cancers of the breast, prostate, and colon, there are serious methodologic issues, including the difficulty in differentiating the effects of dietary fat independent of total energy intake. Reported total fat and saturated fatty acid intakes as a percentage of total energy have been declining over the past 30 years in the United States. Despite this encouraging trend, the majority of individuals--regardless of age--do not report consuming a diet that meets the levels of fat and saturated fatty acids recommended by the Dietary Guidelines for Americans. On a relative basis, saturated fat intake has gone down less than has total fat intake. Individuals of all ages who report consuming a diet with < or = 30% of energy from fat consistently have lower energy intakes. Given the increasing rates of obesity in the United States at an earlier and earlier age, dietary fat reduction may be an effective part of an overall strategy to balance energy consumption with energy needs. In each of the age/gender groups reporting consumption of < or = 30% of energy from fat and less than 10% of energy from saturated fatty acids, fat-modified foods play a more important role in their diets than for people who are consuming higher levels of fat and saturated fat. The data are clear than fat-modified foods make a more significant contribution to diets of consumers with low-fat intakes. While one cannot argue cause and effect from the results presented, the patterns of fat-modified foods/low-fat intakes are consistent. The focus on overall diet quality is often lost in the national obsession with lowering fat inta

The role of breakfast in nutrient intake of 5- to 12-year-old children.

From 7-day food diaries of a cross-sectional sample of American children (n = 657), breakfast consumption patterns were assessed and related to average daily nutrient intake patterns. Results indicated that few of the children skipped breakfast and that breakfast consumption made a significant contribution to the average child's daily nutrient intake. Further, children who had ready-to-eat cereals at breakfast three or more times during the 1-wk period were found to have consumed significantly less (p less than 0.001) fat and cholesterol and significantly more (p less than 0.001) fiber, thiamin, niacin, riboflavin, iron, folacin, pyridoxine, and vitamins B12, A and D than those who had no ready-to-eat cereal at breakfast. Average total daily intakes of the same groups had fewer significant differences. Comparison of the average nutrient composition of the three types of consumed breakfasts revealed that the average breakfast containing presweetened or nonsweetened ready-to-eat cereal had a higher content of sixteen nutrients and a lower content of five nutrients than did the average breakfast including no ready-to-eat cereal.

Functional correlates of Na+,K+-ATPase in lean and obese (ob/ob) mice.

Concentrations of Na+,K+-ATPase enzyme units are lower in skeletal muscle and liver of adult obese (ob/ob) mice than in their lean counterparts. The present studies were designed to provide information on functional correlates of Na+,K+-ATPase in ob/ob mice. Obese mice had lower potassium (K+) content in muscle and liver and higher sodium (Na+) content in muscle and liver and higher sodium (Na+) content in muscle than lean counterparts. The calculated intracellular Na+/K+ ratio in muscle of obese mice was approximately twice as high as in muscle of lean mice. Oxygen consumption was measured in mice maintained at 14 degrees, 25 degrees, or 33 degrees for 40 min and injected with 0.3 or 0.9 microgram ouabain per g body weight. Ouabain, a specific inhibitor of Na+,K+-ATPase, decreased oxygen consumption less in obese mice (12%--25%) than in lean mice (19%--38%). These results suggest that Na+ pump activity may be reduced in obese mice.

Food eating patterns and health: a reexamination of the Ten-State and HANES I surveys.

Dietary, clinical, and biochemical data from the Ten-State Nutrition Survey (1968 to 1970) and the Health and Nutrition Examination Survey I (1971 to 1974), have been reexamined by factor analysis to focus attention on eating patterns as a means of relating food intake to health. The seven statistically different eating patterns generated were characterized by disproportionate consumption of different food groups. The relationship between the combination of foods that people ate and the state of their nutritional health was examined for both samples in total, and for various age, sex, race, region, and income groups within the Health and Nutrition Examination Survey I sample. Significantly different associations between the seven eating patterns and the absence of clinical symptoms and biochemical deficiencies were found. Some eating patterns consistently stood out as being significantly better or worse in this regard (p less than 0.05). This food eating pattern model should prove useful for 1) examining the association between food consumption and the incidence of disease states, such as obesity, hypertension, cardiovascular disease, cancer, and periodontal disease for various large scale dietary-health surveys, 2) establishing food regulatory policies, 3) setting national dietary goals, and 4) educating the public on nutrition and health issues.

Development of lipogenesis and insulin sensitivity in tissues of the ob/ob mouse.

Lipogenesis and insulin sensitivity are evaluated in adipose tissue, liver, and diaphragm of ob/ob and non-ob/ob mice. In ob/ob mice, hepatic fatty acid synthesis from [U-14C]glucose is elevated by 4 wk of age, and adipose tissue fatty acid synthesis increases at approximately 7 wk. Hepatic activities in ob/ob mice of glucose-6-phosphate dehydrogenase (EC 1.1.1.49), 6-phosphogluconate dehydrogenase (EC 1.1.1.44), malate dehydrogenase (EC 1.1.1.40), and alpha-glycerophosphate dehydrogenase (EC 1.1.1.8) are dramatically increased by 7 wk of age. Diminished insulin-stimulated glycogen synthesis is first noted in the diaphragm of ob/ob mice at 7 wk of age. Insulin-stimulated glycogen synthesis in adipose tissue of ob/ob mice is impaired at 3 wk. At 7 wk, insulin-stimulated fatty acid synthesis in adipose tissue of ob/ob mice is markedly increased. Adipose tissue glyceride-glycerol synthesis continues to increase throughout development, whereas fatty acid synthesis decreases after 7 wk. The data suggest that alterations in lipid synthesis occur very early in the development of ob/ob mouse, prior to expression to overt obesity, at which time a major contribution to lipogenesis is made by the liver. The altered de novo lipogenesis does not precede the reported diminution in energy metabolism.

Protein intake regulation and nitrogen retention in young obese and lean mice.

Young female obese (ob/ob) and lean mice were fed a single diet containing 10 or 20% casein or were allowed to self-select from two diets containing 10 and 50, 20 and 60, or 30 and 70% casein for 3 weeks. Obese and lean mice offered a choice of two diets varying in protein-consumed 36% and 32%, respectively, of energy from protein. Although both obese and lean mice consumed more protein when allowed to self-select, each group maintained the same energy intake as observed when a single diet was fed. Because obese mice consumed more energy than lean mice, their self-selected intake of protein was 55% greater than observed in lean mice. The increased protein intake in self-selected obese mice was associated with a decreased tryptophan:large neutral amino acid ratio in their plasma. Average nitrogen retention was only slightly less in obese mice than in lean mice, but the sites of nitrogen deposition differed considerably. Obese mice retained only 35% of their nitrogen in the carcass (skeletal muscle and skeleton) while lean mice retained 58% of their nitrogen in the carcass. In summary, young obese mice allowed to self-select from two diets varying in protein and carbohydrate consumed more protein and more energy, but deposited less nitrogen in their carcasses, than lean mice. Hyperphagia in young obese mice is not directly linked to an increased demand for dietary protein.

Changes in body composition of adult obese (ob/ob) and lean mice fed restricted levels of diets high in carbohydrate, fat or protein.

Adult obese (ob/ob) and lean male mice were fed severely-restricted amounts (approximately 20 to 30 per cent of ad-libitum intake) of either a high-carbohydrate, high-fat or high-protein diet for three weeks. All mice were fed an equal amount of metabolizable energy. Total body fat, total body nitrogen and skeletal-muscle nitrogen were measured in separate groups of mice initially and following three weeks of energy restriction. Obese mice lost 38 to 75 per cent more body energy than did lean mice. Fat accounted for most of the total energy lost (80 to 95 per cent). Obese mice lost more fat, but less protein, than lean mice. Of the total body protein lost by lean mice, 40 to 50 per cent was from skeletal muscle; but obese mice lost very little skeletal-muscle protein. Composition of the diet fed did not significantly affect losses of body weight, fat or protein in either obese or lean mice; mice fed the high-protein diet had heavier livers and kidneys. These results suggest that adult obese mice expend more total energy than lean mice. In addition, loss of body protein during restricted energy intake may be more closely related to remaining body fat stores than to composition of the diet.

Na+,K+-ATPase enzyme units in lean and obese (ob/ob) thyroxine-injected mice.

The possible involvement of Na+,K+-ATPase in the etiology of obesity in the obese (ob/ob) mouse was explored. The number of Na+,K+-ATPase enzyme units in skeletal muscle, liver, and kidneys from 4- and 8-wk-old obese and lean mice was estimated from saturable [3H]ouabain binding to particulate fractions. Neither phenotype nor age altered the Kd value for ouabain binding in these three tissue preparations. The total number of [3H]ouabain binding sites in hindlimb muscles was 35--55% lower in 4- and 8-wk-old obese mice than in their lean counterparts. However, the total number of [3H]ouabain binding sites in liver and kidneys of obese mice was similar to values observed in their lean counterparts. Because it has been suggested that ob/ob mice are hypothyroid, we investigated the response of Na+,K+-ATPase in these mice to thyroid hormone treatment (approximately 5 microgram thyroxine/day for 2 wk). The number of [3H]ouabain binding sites in the three tissues increased in both obese and lean mice injected with this relatively large dose of thyroxine, but the obese mice were 2--3 times more responsive than lean mice.

Maintenance energy requirements, energy retention and heat production of young obese (ob/ob) and lean mice fed a high-fat or a high-carbohydrate diet.

Female obese (ob/ob) and lean mice were weaned at 21 days of age, placed in wire-mesh cages maintained at 25 to 30 degrees, and fed a high-fat or a high-carbohydrate diet for 21 days. The body energy balance procedure was utilized to determine the maintenance energy requirements, and the efficiency of dietary energy utilization, above maintenance, in these mice. Heat production of each mouse was measured weekly in a gradient-layer calorimeter. Regressions of changes in body energy per kg3/4 on metabolizable energy intake per kg3/4 indicated that the maintenance energy requirement averaged 72 kcal/kg3/4/day for obese mice and 124 kcal/kg3/4/day for lean mice. Diet composition did not influence the maintenance energy requirements, but utilization of energy, above maintenance, in obese mice fed the high-fat diet was 41% more efficient than observed in obese mice fed the high-carbohydrate diet and 38 to 71% more efficient than observed in lean mice. Heat production, per unit body weight was lower in obese mice than in lean mice. The lowest heat production was observed in obese mice fed the high-fat diet. The 40% lower maintenance energy requirement of the obese mice is a major factor contributing to the high efficiency of energy retention in these mice. Consumption of a high-fat diet further improved the ability of the obese mice to retain dietary energy.