Measuring intake in free-living human subjects: a question of bias.
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Bias↗
Biomedical subjects
B L Heitmann
Publications and source records attributed to B L Heitmann.
Food patterns, flour fortification, and intakes of calcium and vitamin D: a longitudinal study of Danish adults.
STUDY OBJECTIVE: Deficiencies in calcium and vitamin D intakes are involved in the aetiology of osteoporosis, and health authorities recommend that the population consume a diet providing sufficient calcium and vitamin D. However, in 1987 the Danish Government withdrew a mandatory fortification of flour with calcium. This study examines intakes of calcium and vitamin D over time, in relation to food patterns, recommendations, and legislation. DESIGN: Food and nutrient intakes were measured by a short food frequency questionnaire (FFQ) and a thorough diet history interview, in 1987/88, and again six years later. SETTING: Copenhagen County, Denmark. PARTICIPANTS: 329 men and women, aged 35-65 years at first examination in 1987/88. RESULTS: At both examinations the non-enriched median intakes of calcium in men as well as women were above the recommended 600 mg/day. However, apparently the fortification of flour supplied up to 30% of the total calcium intake, and without the mandatory fortification, the percentage of adults with intakes below this recommendation increased from 6% to 22%. This group of subjects consumed cheese, milk, and oatmeal less often than those who had calcium intakes over 600 mg/day. During the study period the median intakes of vitamin D, which were well below the recommended 5 micrograms/day, did not change significantly. Associations between foods and vitamin D intakes were, in general, weak and insignificant, except for a positive association with fish intake. CONCLUSIONS: Data on calcium intakes suggest that the decision to stop the mandatory fortification of flour with calcium may have been premature. The short FFQ may be used for a rough classification of people in relation to their calcium intake, while this method seems insufficient for ranking vitamin D intakes.
Adult↗
[Significance of intentional weight loss on health].
The aim of the present study was critically to review how intentional weight loss in overweight and obesity influences mortality. No randomized weight loss intervention trial has included mortality as an end-point. However, even minor weight loss causes beneficial changes in risk factors for cardiovascular disease, whereas the vast majority of observational studies have linked weight loss to excess mortality. Most observational studies do not have information on intentionality of weight loss and suffer from other methodological limitations making inferences from these studies difficult. Given the available observational evidence, the possibility that intended weight loss may cause some increased mortality cannot be excluded. However, considering the totality of the evidence on effects of intended weight loss among overweight and obese subjects, there may be other benefits, such as: psycho-social and physical well-being, risk factor improvement, decreased morbidity, and in certain high-risk subgroups decreased mortality. Treatment of obesity is therefore recommended, particularly in the presence of risk factors or complications.
Health Status↗
[How valid are self-reported intakes of beer, wine and spirits in population studies?].
In order to compare data on intake of wine, beer and spirits from a frequency questionnaire with intake of each type of alcoholic beverage estimated from a dietary interview, a randomly selected sub-sample of 244 women and 249 men aged 35-65 years was cross-sectionally studied. The sample was a sub-sample of the Danish MONICA study. Mean outcome measure in the study was the differences in intake of beer, wine and spirits as reported by the frequency questionnaire and the diet history interview. We found an overall agreement between the two methods, with very little or no systematic variation for all three alcoholic beverages. We conclude that compared to a more time and money consuming thorough dietary interview, the traditional frequency questionnaires seem to sufficiently capture intakes of different types of alcohol. Bias in alcohol reporting by the frequency questionnaire does not seem responsible for the recently found decreased mortality among subjects with a daily intake of wine, nor the increased mortality from drinking of spirits.
Adult↗
Low-fat diets may prevent weight gain in sedentary women: prospective observations from the population study of women in Gothenburg, Sweden.
The Population Study of Women in Gothenburg, Sweden is an ongoing prospective study of female residents who were recruited from the local registry in 1968-1969 when they were 38-60 years old. The data presented here were collected from 361 healthy women who underwent a baseline physical examination including a supplementary dietary history interview and returned for a second general health examination 6 years later. This report identifies a subgroup of 57 women who were sedentary during their leisure time and appear to have been particularly susceptible to gaining weight as a function of the fat content of their diets. Specifically, longitudinal analysis of body weights in the whole sample revealed a statistical interaction between leisure-time physical activity and habitual dietary fat intake (energy%), as reported at the baseline examination, in the prediction of subsequent weight change. Further stratified analysis suggested that weight changes were significantly dependent on dietary fat intake among the sedentary women only. High energy intake also predicted weight gain in the sedentary group, although the predictive value for a high-fat diet was of marginal significance after adjusting for total energy consumption. These results suggest that sedentary recreational activity plus a low-fat diet may have a combined contribution to weight change that is not equivalent to the sum of the separate effects. Such a synergy between two modifiable lifestyle factors seems highly relevant for prevention of obesity.
Adult↗
Food patterns associated with intakes of fat, carbohydrate and dietary fibre in a cohort of Danish adults followed for six years.
OBJECTIVE: To examine associations between food consumption patterns, measured by a short food frequency questionnaire (FFQ), and the intakes of fat, carbohydrates and fibre over time, and in relation to recommended guidelines. DESIGN: The same 329 individuals had their diet intake measured by a short FFQ and a thorough diet history interview, first in 1987/88, and again six years later in 1993/94. SETTING: The County of Copenhagen, Denmark. SUBJECTS: Three hundred and twenty-nine men and women, aged 35-65 y selected randomly from a large population sample. RESULTS: At both examinations fat energy displayed the strongest positive associations with the intake of animal fats and negative correlations with the vegetables. These food items explained most of the total explained variation in fat intake. In general the associations between food items and intakes of carbohydrates and fibre were similar but inverse, to those found for fat. During the study period median fat energy decreased from 41-38%. A less frequent intake of animal fats over time predicted an increase in fat energy both among men and women, while a more frequent intake of fruit and pasta, and a less frequent intake of cakes was associated with an increase in dietary fibre. CONCLUSIONS: Food items like animal fats, vegetables and certain high starch foods can predict compliance to dietary guidelines for fat and carbohydrates. The study also shows that the food pattern of this Danish cohort has changed in the direction of a more healthy diet during the six years of follow-up. SPONSORSHIP: This study was granted by the Danish Agricultural and Veterinary and Danish Medical Councils and the Danish Health Insurance foundation.
Adult↗
Ten year trends in the dietary habits of Danish men and women. Cohort and cross-sectional data.
OBJECTIVE: To describe 10 year trends and individual changes in food habits of Danish men and women in relation to dietary recommendations using data from both a cohort and a repeated cross-sectional study, and to examine whether the two sampling methods give similar results. DESIGN: Baseline data were collected in 1982-1984 and respectively repeated measurements for cohort and cross-sectional changes in food habits. SETTING: The County of Copenhagen, Denmark. SUBJECTS: Men and women aged 30-70y in 1982-1984, 1986-1988 and 1992-1994. The trend analyses included 3785 subjects for cohort and 7316 for cross-sectional study, respectively. Longitudinal changes were studied among 2430 individuals with food data from all three examinations. METHODS: Food intakes were estimated using a short food frequency questionnaire. RESULTS: During the study period both men and women reported a decreased intake frequency of animal and vegetable fats, milk, eggs, meat products, white bread and potatoes, while they had increased intakes of low-fat margarine, fruit, raw vegetables, coarse breads, oatmeal, pasta, rice, cakes and candy. In both men and women the decrease in the consumption frequency of, white bread and potatoes, and the increase in pasta, and candy, were higher in the younger than in the older age group. In contrast, the increased consumption frequency of coarse breads, and oatmeal were most pronounced in the older age groups. For most foods the cohort and the repeated cross-sectional surveys gave similar results. CONCLUSIONS: From 1982 through 1994 the food habits of middle-aged Danish men and women changed in the direction of a more healthy diet as recommended by health authorities. With the limitation of a possible reporting bias both the cohort and repeated cross-sectional study designs may be used for monitoring changes in food intake.
Adult↗
Are there ethnic differences in the association between body weight and resistance, measured by bioelectrical impedance?
OBJECTIVE: To describe ethnic differences in the relationship between body size and body composition. Knowledge about such differences is important when studying obesity-related complications, such as hypertension and non-insulin dependent diabetes, because it may not be possible to generalize results from one study population to other populations. DESIGN: Cross-sectional study. SUBJECTS: Four groups of different ethnic identity (2987 Caucasians (Danes), 243 predominantly Melanesian (Torres Strait Islanders from northern Australia), 206 Australian Aborigines and 146 Polynesians (New Zealand Samoans), aged 30-70 y, were studied. MEASUREMENTS: We examined associations between body weight and bioelectrical impedance, as a measure of body composition. RESULTS: Except for Australian Aborigines, associations (slopes) between body weight and resistance were generally constant in the different ethnic groups, once height and age differences had been considered, indicating that this relationship may involve a certain universality, that is independent of the population specificity for impedance measurement. Systematic differences in instrument readings or electrodes did not seem to be responsible for the differences found. CONCLUSION: With the exception of Australian Aborigines, there may be a constant relation between body size and body composition (total body water or fat free mass) of different ethnic groups, that depends on gender and age category only.
Adult↗
Are genetic determinants of weight gain modified by leisure-time physical activity? A prospective study of Finnish twins.
A large number of studies have shown that obesity is both under genetic control and influenced by several environmental factors, including energy expenditure and intake. Several studies in animals and humans have furthermore suggested that certain environmental factors, such as a high fat intake, may modify the expression of the genes responsible for weight gain. The present study examined whether physical activity, measured at the baseline examination in 1975, was likely to play a differential role in subsequent weight changes in the following 6 y in 1571 monozygotic and 3029 dizygotic, same-sex twin pairs from the Finnish Twin Cohort Study. A hierarchical multiple-regression analysis was used to test for gene-environment interactions by identifying significant three-way interactions between genetic factors, physical activity, and weight change. The results showed that associations between weight change in twin A and twin B were significantly stronger for monozygotic than for same-sex dizygotic twins at all levels of physical activity. Additionally, in the monozygotic men the strength of the association varied with physical activity level, and the association between the change in body mass index between the twin pairs with the highest physical activity level was about three times stronger (beta = 0.40) than the association in twin pairs with the lowest physical activity level (beta = 0.15, P for trend = 0.002). In pairs of dizygotic men, and in both monozygotic and dizygotic women, similarity in body mass index change was independent of physical activity level (all P > 0.14). The present study showed that genetic factors may modify the effects of physical activity on weight change, and suggests that a sedentary lifestyle may have an obesity-promoting effect in men with a genetic predisposition.
Adult↗
[Obese individuals underestimate their food intake--which food groups are under-reported?].
The purpose of the study was to examine the distribution of macronutrient density patterns in relation to obesity. This was done in a sample of 323 Danish men and women aged 35-65 years, selected randomly from a larger population sample of adult Danes. Dietary reporting bias of energy and protein intake, in relation to body fat percentage, was assessed by comparing intake data from a diet history interview with data estimated from PABA-validated 24-hour nitrogen excretion and estimated 24-hour energy expenditure. The results of the study showed that degree of obesity was positively associated with protein underreporting of total energy and protein, whereas compared with total energy reported, protein was overreported by the obese subjects. These associations were evident despite control for gender, age and smoking (p = 0.0003). In conclusion, errors in dietary reporting of protein seem to occur disproportionately with respect to total energy, suggesting a differential reporting pattern of different foodstuffs. Although, on average, all subjects over-reported energy percent from protein, over-reporting was most common in obese. It may therefore be speculated that snack type foods are preferentially forgotten when dietary omission occurs in obese individuals. The results of the present study seem in agreement with the general assumption that obese subjects tend to specifically under-report fat and sugar-rich foods, rather than generally under-report their total intake. These results may have wide implications for the interpretation of studies of diet and comorbidities to obesity.
Adult↗
Immunological methods for dosimetry of heterocyclic amines.
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Adult↗
Relationship between dietary iron intake, corrected for diet reporting error, and serum ferritin in Danish women aged 35-65 years.
Several studies have failed to demonstrate an association between Fe status and intake of dietary Fe. However, in the long term, it seems logical to presume that body Fe reserves are, fundamentally, dependent on the intake of bioavailable dietary Fe. This discrepancy may depend on several factors: (1) interindividual variation in biological availability of dietary Fe (differences in intestinal absorption), (2) interactions between dietary Fe and absorption enhancers and inhibitors, (3) variations in physiological (menstruation, childbirth) or unphysiological (blood donation) Fe losses, (4) the failure to adjust dietary intake data for Fe supplements, (5) uncertain food composition data (discrepancies between calculated and chemically measured Fe content in the diet), and (6) diet reporting error (reported intake of dietary Fe may deviate considerably from the true intake). The present study examined associations between dietary intake of Fe (assessed by diet history interview) and Fe status (assessed by ferritin status) among 167 Danish women aged 35-65 years, who were not blood donors, by taking into account diet reporting error (assessed from p-amino benzoic acid-validated urinary N), physiological blood losses (menstruation, childbirth, abortions), and Fe supplementation. Our results indicate that the lack of a general association between Fe status and dietary Fe intake may, in part, be caused by selective diet reporting error.
Adult↗
Social desirability bias in dietary self-report may compromise the validity of dietary intake measures. Implications for diet disease relationships.
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Diet Surveys↗
The validity of a short food frequency questionnaire and its ability to measure changes in food intake: a longitudinal study.
BACKGROUND: In studies of health behaviour exploring factors associated with differences and changes in eating patterns of populations, diet is often measured with short food frequency questionnaires (FFQ). This study examines the validity of a short FFQ by comparing frequencies of food intake from the FFQ to information on food intake obtained by a diet history interview. METHODS: Food intake was measured at two separate occasions in the same 329 individuals, first in 1987-1988 and 6 years later in 1993-1994. RESULTS: In 1987-1988 the Spearman correlation coefficients were around r = 0.50 for most foods, with white and dark ryebread and light bread as extremes on the one hand (r = 0.10, r = 0.23 and r = 0.27, respectively) and coarse bread, fruit and cakes as extremes on the other (r = 0.61, r = 0.60, r = 0.60, respectively). In general, the correlations were higher at the second data collection in 1993-1994. At both data collections, the mean food intake from the diet history interview increased with increasing frequency category, indicating that the questionnaire was able to identify levels of food intake correctly. In general, when individual changes in food intake were assessed during the study period, those who reported a less frequent intake by the FFQ in 1993-1994 compared with 1987-1988 also had a lower mean daily intake according to the diet history information. CONCLUSION: The short FFQ can quantify food intakes and, is also responsive to changes in food intake over time. Thus the short FFQ can be used to monitor changes in food patterns at a group level.
Adult↗
Comparison of body composition by dual energy X-ray absorptiometry to other estimates of body composition during weight loss in obese patients with rheumatoid arthritis.
Body composition was determined by dual energy X-ray absorptiometry (DXA) scanning and classical reference methods (40K, 3H2O, and a combination of these in a four-compartment model) in 19 overweight patients with rheumatoid arthritis who underwent a 12-week weight-reducing regimen. The aim of the study was to investigate whether DXA provides a valid estimate of body composition. The results showed that weight as determined by DXA was highly significantly correlated to weight determined by scales. Furthermore, significant correlations were found in the body components (fat-free mass, fat mass) determined by DXA, 40K, 3H2O and the four-compartment model. Mean values differed slightly but significantly. With respect to changes in body composition, no significant correlations were found between any of the methods, except for the weight loss recorded by DXA and scales, and loss of fat mass (and fat free mass) estimated by 3H2O and the four-compartment model. The sparseness of correlations reflected the small changes in fat-free mass and fat mass (2.6 and 1.7 kg respectively), and the fact that changes were comparable to measurement errors of the various methods. We suggest that DXA scanning is a valid supplement for determination of body composition. Validation of DXA scanning requires new experimental in vitro investigations, which, incidentally, also applies to the classical reference methods.
Absorptiometry, Photon↗
Validity of self-reported intakes of wine, beer and spirits in population studies.
OBJECTIVE: To compare data on intake of wine, beer and spirits from a frequency questionnaire with intake of each type of alcoholic beverage estimated from a dietary interview. DESIGN: Cross-sectional study. SETTING: The Danish MONICA study. SUBJECTS: A randomly selected sub-sample of 244 women and 249 men aged 35-65 y. MAIN OUTCOME MEASURE: Differences in intake of beer, wine and spirits as reported by the frequency questionnaire and the diet history interview. RESULTS: There was an overall agreement between the two methods, with very little or no systematic variation for all three alcoholic beverages. CONCLUSION: Compared to a more time consuming and thorough dietary interview, the traditional frequency questionnaires seem to sufficiently capture intakes of different types of alcohol. Bias in alcohol reporting by the frequency questionnaire does not seem responsible for the recently found decreased mortality among subjects with a daily intake of wine, nor the increased mortality from spirits drinking.
Adult↗
Dietary underreporting by obese individuals--is it specific or non-specific?
OBJECTIVE: To examine the distribution of patterns of macronutrient density in relation to obesity. DESIGN: Cross sectional. SETTING: Denmark. SUBJECTS: 323 men and women aged 35-65 years, selected randomly from a larger population sample of Danish adults. MAIN OUTCOME MEASURE: Bias in dietary reporting of energy and protein intake in relation to percentage body fat, assessed by comparison of data from an interview on dietary intake with data estimated from 24 hour nitrogen output, validated by administering p-aminobenzoic acid, and estimated 24 hour energy expenditure. RESULTS: Degree of obesity was positively associated with underreporting of total energy and protein, whereas compared with total energy reported, protein was overreported by the obese subjects. CONCLUSION: Errors in dietary reporting of protein seem to occur disproportionately with respect to total energy, suggesting a differential reporting pattern of different foods. Although, on average, all subjects showed a greater underreporting of energy than of protein, this was most common in the obese subjects. Snack-type foods may be preferentially forgotten when obese people omit food items in dietary reporting. These results seem to agree with the general assumption that obese people tend to underreport fatty foods and foods rich in carbohydrates rather than underreport their total dietary intake. These results may have implications for the interpretation of studies of diet and comorbidities related to obesity.
4-Aminobenzoic Acid↗
Dietary fat intake and weight gain in women genetically predisposed for obesity.
The influence of dietary fat intake on subsequent change in body mass index (BMI) of adult women was examined while taking into account predisposition for obesity. A representative population sample of 361 Swedish women aged 38-60 y was first examined in 1968-1969 and followed up 6 y later. Dietary intake was estimated by diet history interview, and parental fatness was assessed by questionnaire. Women already overweight with > or = 1 obese parent were considered predisposed to obesity. When total energy intake, smoking habits, physical activity, and menopausal status were controlled for in regression analysis, high dietary fat intake was significantly associated with a 6-y gain in BMI only the predisposed women (P = 0.003), but not among obese women with lean parents, or lean women with or without obese parents. High dietary fat intake may have an obesity-promoting effect in women with a genetic predisposition.
Adult↗