Evaluation of long-term dietary intakes of adults consuming self-selected diets

Maintenance of Lost Weight and Long-Term Management of Obesity

Weight loss can be achieved through a variety of modalities, but long-term maintenance of lost weight is much more challenging. Obesity interventions typically result in early weight loss followed by a weight plateau and progressive regain. This review describes current understanding of the biological, behavioral, and environmental factors driving this near-ubiquitous body weight trajectory and the implications for long-term weight management. Treatment of obesity requires ongoing clinical attention and weight maintenance-specific counseling to support sustainable healthful behaviors and positive weight regulation.

Short and long-term energy intake patterns and their implications for human body weight regulation

Adults consume millions of kilocalories over the course of a few years, but the typical weight gain amounts to only a few thousand kilocalories of stored energy. Furthermore, food intake is highly variable from day to day and yet body weight is remarkably stable. These facts have been used as evidence to support the hypothesis that human body weight is regulated by active control of food intake operating on both short and long time scales. Here, we demonstrate that active control of human food intake on short time scales is not required for body weight stability and that the current evidence for long term control of food intake is equivocal. To provide more data on this issue, we emphasize the urgent need for developing new methods for accurately measuring energy intake changes over long time scales. We propose that repeated body weight measurements can be used along with mathematical modeling to calculate long-term changes in energy intake and thereby quantify adherence to a diet intervention and provide dynamic feedback to individuals that seek to control their body weight.

Patterns in food intake correlate with body mass index

Quantifying eating behavior may give clues to both the physiological and behavioral mechanisms behind weight regulation. We analyzed year-long dietary records of 29 stable-weight subjects. The records showed wide daily variations of food intake. We computed the temporal autocorrelation and skewness of food intake mass, energy, carbohydrate, fat, and protein. We also computed the cross-correlation coefficient between intake mass and intake energy. The mass of the food intake exhibited long-term trends that were positively skewed, with wide variability among individuals. The average duration of the trends (P = 0.003) and the skewness (P = 0.006) of the food intake mass were significantly correlated with mean body mass index (BMI). We also found that the lower the correlation coefficient between the energy content and the mass of food intake, the higher the BMI. Our results imply that humans in neutral energy balance eating ad libitum exhibit a long-term positive bias in the food intake that operates partially through the mass of food eaten to defend against eating too little more vigorously than eating too much.

Markers of the validity of reported energy intake

Energy intake (EI) is the foundation of the diet, because all other nutrients must be provided within the quantity of food needed to fulfill the energy requirement. Thus if total EI is underestimated, it is probable that the intakes of other nutrients are also underestimated. Under conditions of weight stability, EI equals energy expenditure (EE). Because at the group level weight may be regarded as stable in the timescale of a dietary assessment, the validity of reported EI can be evaluated by comparing it with either measured EE or an estimate of the energy requirement of the population. This paper provides the first comprehensive review of studies in which EI was reported and EE was measured using the doubly labeled water technique. These conclusively demonstrate widespread bias to the underestimation of EI. Because energy requirements of populations or individuals can be conveniently expressed as multiples of the basal metabolic rate (BMR), EE:BMR, reported EI may also be expressed as EI:BMR for comparison. Values of EI:BMR falling below the 95% confidence limit of agreement between these two measures signify the presence of underreporting. A formula for calculating the lower 95% confidence limit was proposed by Goldberg et al. (the Goldberg cutoff). It has been used by numerous authors to identify individual underreporters in different dietary databases to explore the variables associated with underreporting. These studies are also comprehensively reviewed. They explore the characteristics of underreporters and the biases in estimating nutrient intake and in describing meal patterns associated with underreporting. This review also examines some of the problems for the interpretation of data introduced by underreporting and particularly by variable underreporting across subjects. Future directions for research are identified.

Carbohydrate ingestion, blood glucose and mood

A series of studies have reported that a high carbohydrate meal, or diets high in carbohydrate, were associated with feeling less energetic. However, after a drink containing pure sugar most studies report no effect. Meals almost exclusively carbohydrate increase the availability of tryptophan and hence serotonin synthesis in the brain, however, a small amount of protein blocks this mechanism making it an uncommon response. In many individuals, poor mood stimulates the eating of palatable high carbohydrate/high fat foods that stimulate the release of endorphins. There is a tendency for those with lower blood glucose, when performing cognitively demanding tasks, to report poorer mood. In a range of situations an association between a tendency for blood glucose levels to fall rapidly, and irritability, has been found. Differences in the ability to control blood glucose levels influence the association between carbohydrate intake and mood. There is a need in future research to contrast the impact of carbohydrate on mood in those distinguished because of their pre-existing psychological and physiological functioning.

[Dietary sources of vitamin A, C, E and beta-carotene in a adult Mediterranean population]

OBJECTIVE

Estimation of vitamin A, C, E and beta-carotene food sources, as well as its nutritional intake and density in adult Catalonian population.

METHODOLOGY

A cross-sectional study was conducted over 2,346 individuals obtained from the sample of Catalonian Survey of Nutritional Status aged 18 to 75 years old to estimate usual dietary intake of vitamins A, C, E and beta-carotene using two 24 hour dietary recalls administered in two periods (june-july and november-december of 1992). Replicated 24 hour Recalls allowed for estimation of usual intake. Calculation of food sources for vitamins encompassed three phases: foods transformation into nutrients, aggregation of foods in categories and sum of nutrients by food categories.

RESULTS

Intake of vitamin A (equivalents of retinol of provitamin A and vitamin A), E, C were closely near or higher than RDA. Nutritional density of vitamin C, E and beta-carotene were higher in female group. Nutritional density was positively associated to age for vitamins C, E and beta-carotene. Addition fat was the first source of vitamin E and it reached 33.8% of total vitamin E intake. Vegetables contributed in 17.3 % to the total vitamin C, whereas fruits accounted for 57.9%. Fruits recached 40.6% of the total beta-carotene intake, whereas vegetables accounted for 34.8%. The major contributors of vitamin A were milk and dairy products.

CONCLUSIONS

Nutritional intake of vitamin A, C and E are over the RDA parameters suggesting an healthy nutritional status that must be confirmed and ratify by biochemical assessment. Nutritional densities were higher in female gender than in males in vitamins C, E, and beta-carotene possibly due to a higher intake of total lipids in male gender than in females. Nutritional density was positively associated to age in the same group of vitamins, suggesting a higher intake of empty calories in younger group. Fruits and Vegetables accounted for more than 70% of vitamin C and beta-carotene and major contributors were citrics, carrots, tomatoes, spinach, and cauliflower, highlighting their importance in elaboration of dietary guide lines.

Helping elderly participants keep 3-day diet records in the New Mexico Aging Process Study

Although verbal and written instructions on how to record dietary intake are commonly used in research, little information has been published describing instructional methods or materials. In the New Mexico Aging Process Study, a longitudinal study of nutrition and aging, participants keep a 3-day diet record each year. Classroom instruction and written materials are used in the study, and they were updated for use with Food Intake Analysis System (FIAS), version 2.3. This article describes the instructional methods and materials used to prepare elderly participants to keep accurate diet records; reports the development of a novel instructional tool, the food description flowcharts; and presents participants' opinions of the quality of the instruction and the usefulness of written materials. Included in the written materials were general instructions for recording food intake, examples of completed food intake and recipe forms, hints for eating out, and instructions for easy-to-use electronic scales. The flowcharts guide participants in accurately describing food intake while matching the coding requirements of FIAS. Fifty participants completed a written survey to evaluate the instructions and written materials. More than half of the respondents found the written materials to be very useful. All found the verbal instruction to be excellent or good. Nutritionists observed that records kept by participants who attended the class were generally complete and specific. The findings indicate that participants were satisfied with the instructions and written materials.

Brain serotonin, carbohydrate-craving, obesity and depression

Serotonin-releasing brain neurons are unique in that the amount of neurotransmitter they release is normally controlled by food intake: Carbohydrate consumption--acting via insulin secretion and the "plasma tryptophan ratio"--increases serotonin release; protein intake lacks this effect. This ability of neurons to couple neuronal signaling properties to food consumption is a link in the feedback mechanism that normally keeps carbohydrate and protein intakes more or less constant. However, serotonin release is also involved in such functions as sleep onset, pain sensitivity, blood pressure regulation, and control of the mood. Hence many patients learn to overeat carbohydrates (particularly snack foods, like potato chips or pastries, which are rich in carbohydrates and fats) to make themselves feel better. This tendency to use certain foods as though they were drugs is a frequent cause of weight gain, and can also be seen in patients who become fat when exposed to stress, or in women with premenstrual syndrome, or in patients with "winter depression," or in people who are attempting to give up smoking. (Nicotine, like dietary carbohydrates, increases brain serotonin secretion; nicotine withdrawal has the opposite effect.) It also occurs in patients with normal-weight bulimia. Dexfenfluramine constitutes a highly effective treatment for such patients. In addition to producing its general satiety-promoting effect, it specifically reduces their overconsumption of carbohydrate-rich (or carbohydrate-and fat-rich) foods.

Modification of liver fatty acid metabolism in mice by n-3 and n-6 delta 6-desaturase substrates and products

The effects of dietary supplementation of either alpha-linolenic acid (18:3(n-3)) or stearidonic acid (18:4(n-3)) in combination with either linoleic acid (18:2(n-6)) or gamma-linolenic acid (18:3(n-6)) on liver fatty acid composition in mice were examined. Essential fatty acid deficient male C57BL/6 mice were separated into four groups of seven each and were fed a fat-free semi-purified diet supplemented with 1% (w/w) fatty acid methyl ester mixture (1:1), 18:2(n-6)/18:3(n-3), 18:2(n-6)/18:4(n-3), 18:3(n-6)/18:3(n-3), or 18:3(n-6)/18:4(n-3). After 7 days on the diets, fatty acid compositions in liver phosphatidylcholine and phosphatidylethanolamine fractions were analyzed. In groups fed 18:4(n-3) (18:2(n-6)/18:4(n-3) or 18:3(n-6)/18:4(n-3)) as compared to those fed 18:3(n-3) (18:2(n-6)/18:3(n-3) or 18:3(n-6)/18:3(n-3)), the levels of 20:4(n-3), 20:5(n-3) and 22:5(n-3) were increased, whereas those of 20:3(n-6) and 20:4(n-6) were decreased. When 18:3(n-6) replaced 18:2(n-6) as the source of n-6 acids, the levels of 18:3(n-6), 20:3(n-6), 20:4(n-6) and 22:5(n-6) were increased, whereas those of 20:4(n-3) and 20:5(n-3) were reduced. Replacing 18:3(n-3) by 18:4(n-3) reduced the (n-6)/(n-3) ratio by approx. 30%, whereas replacing 18:2(n-6) by 18:3(n-6) increased the (n-6)/(n-3) ratio by approx. 2-fold. These findings indicated that delta 6-desaturase products were metabolized more readily than their precursors. Both products also competed for the subsequent metabolic enzymes. However, the n-6 fatty acids derived from 18:3(n-6) were incorporated more favourably into liver phospholipids than n-3 fatty acids derived from 18:4(n-3).

Trace nutrients. 5. Minerals and vitamins in the British household food supply

1. The amounts of magnesium, copper, zinc, phosphorus, manganese, potassium, vitamin B6, vitamin B12, folate, pantothenic acid, biotin, vitamin E and dietary fibre in the British household diet were calculated by applying appropriate values from recent analytical studies to the amounts of foods recorded in the National Food Survey during 1986. 2. National average intakes were (mg/person per d): Mg 247, Cu 1.25, Zn 9.0, P 1249, Mn 3.43, K 2694, vitamin B6 1.73, vitamin B12 6.33 micrograms, folate 230 micrograms, pantothenic acid 6.07, biotin 35 micrograms, vitamin E 8.4. Regional and income-group differences were estimated, and found to be small. Additional contributions from alcoholic drinks and confectionery were also determined. 3. Dietary fibre was estimated both as unavailable carbohydrate and as non-starch polysaccharide. The national average intakes were 21.8 and 12.9 g/d respectively. 4. Intakes were compared with Canadian (Department of National Health and Welfare, 1983) and American (National Research Council, 1980) recommended dietary allowances (RDAs). With the exception of biotin, the Canadian RDAs were met by the household diet but the much higher American RDAs were only met for vitamin B12 and pantothenic acid.

Self-selected vs. controlled diet as a baseline for human studies: effects of nutrient intakes on blood pressure and on constituents of blood and urine

This study demonstrates that a three-week stabilization period, in which all subjects eat an identical diet, produced a more uniform but different baseline of metabolic parameters than the subject's self-selected or "habitual" diets. Subjects required more food energy to maintain initial body weights during the stabilization period than when they ate their reported self-selected diets; average intakes of almost all nutrients were higher from the stabilization than from the self-selected diet. The switch to the stabilization diet produced small but significant reductions in blood pressure, in some serum enzymes, urine volume, and sodium; and statistically significant increases in serum LDL cholesterol, potassium, aldosterone, protein, albumin, phosphorus, BUN, and in urine potassium. The findings indicate that results must be interpreted with caution from studies in which the baseline for measuring metabolic variables is established by feeding subjects a standardized diet that differed markedly from their regular, self-selected diets.