Joseph T. Anderson

DENSITOMETRIC ANALYSIS OF BODY COMPOSITION: REVISION OF SOME QUANTITATIVE ASSUMPTIONS*

One can trace to Archimedes the idea that in a system consisting of two additive components which are mixed but the densities of which are known ( d l , d 2 ) , the determination of the density of the system ( D ) allows one to calculate the proportional masses of the two components. Let’s denote these components as W1 and W2.S Then, in a system with total weight W = W1 + Wz, the general equation for calculating component W1 expressed as a fraction (w1) of the total body weight is:

Serum cholesterol response to changes in the diet: IV. Particular saturated fatty acids in the diet.

For many dietary changes satisfactory prediction of the average change in the serum cholesterol level of man in mg./100 ml., is given by Δ Chol. = 1.35(2ΔS − ΔP) + 1.5ΔZ where S and P are percentages of total calories provided by glycerides of saturated and polyunsaturated fatty acids in the diet and Z2 = mg. of dietary cholesterol/1000 Cal. This formula fails, however, when the dietary change involves large amounts of cocoa butter and discrepancies also appear with beef tallow or hydrogenated coconut oil diets. Controlled dietary experiments at the University of Minnesota and at 2 other centers, provide 63 sets of comparisons of serum cholesterol averages for groups of men on each of 2 chemically characterized diets. Least-squares analysis indicates that stearic acid, as well as saturated fatty acids containing fewer than 12 carbon atoms, have little or no effect on serum cholesterol in man. The equation, Δ Chol. = 1.2(2ΔS′ − ΔP) + 1.5ΔZ, yields good correlation (r = 0.93) with the observed values in these 63 sets of data. This formulation also resolves heretofore puzzling discrepancies in the literature.

Serum cholesterol response to changes in the diet: II. The effect of cholesterol in the diet.

The series of metabolic ward experiments, with 22 physically healthy men in each, covered dietary cholesterol intakes from 50 to 1450 mg. daily, with all other variables controlled. The serum-cholesterol data, plus the data from comparable experiments reported from 4 other institutions, were analyzed in regard to average serum cholesterol response (Δ Chol., mg./100 ml.) to changed cholesterol intake. Least-squares solution, using serum cholesterol responses in 19 sets of dietary cholesterol comparisons, gives Δ Chol. = 1.5(Z2 − Z1), where the subscripts refer to the diets compared and Z is the square-root of the dietary cholesterol, measured as mg./1000 Cal. The correlation between the average Δ Chol. predicted and that observed is r = 0.95. The serum response was the same over a wide range of dietary fat composition. Ordinary American diets range from about about 150 to 350 mg. cholesterol/1000 Cal. These extremes correspond to an average difference of about 9 mg. of cholesterol/100 ml. of serum if all other variables are constant. Change from 250 mg./l000 Cal. to a cholesterol-free diet will cause an average fall of about 24 mg./100 ml. of serum. But a 50 per cent decrease in dietary cholesterol will produce an average decrease in the serum of only about 7 mg./100 ml. For the purpose of controlling the serum level, dietary cholesterol should not be completely ignored but attention to this factor alone accomplishes little.

Serum cholesterol response to changes in the diet: I. Iodine value of dietary fat versus 2S-P.

In men in calorie equilibrium, changes in dietary fat produce responses in the serum cholesterol level that, on the average, are predictable from the percentages of total calories provided by saturated (S) and polyunsaturated (P) fatty acid glycerides in the diets concerned. S and P have opposing actions and, in general, Δ Cholesterol (mg./100 ml.) = 2.7ΔS − 1.3ΔP, where Δ refers to the difference between 2 diets. Increasing the number of double bonds beyond 2 in polyunsaturated fatty acids does not result in proportionate increases in serum cholesterol-lowering effect. The mono-enes oleic and erucic acid have little or no effect on the serum cholesterol level when they are exchanged in the diet for equal calories of simple carbohydrate. Changes of fats in the diet produce serum cholesterol responses that are also correlated with the iodine values, or the square-roots of those values, of the fats concerned when the iodine value happens to be highly correlated with 2.7S - 1.3P. When changes in diet fats involve substantial differences in amounts of mono-enes, or of fatty acids containing more than 2 double bonds, the serum cholesterol response has a low or negligible correlation with the iodine value, or its square-root, of the fats.

Coronary Heart Disease among Minnesota Business and Professional Men Followed Fifteen Years

Relative weight, body fatness (skinfold thickness), blood pressure, and serum cholesterol are reported from 281 Minnesota business and professional men, initially clinically healthy and aged 45 to 55, who were followed by annual examinations since the winter of 1947–48. In 15 elapsed years, coronary heart disease developed definitely in 32 men and possibly in 16 other men.The incidence of coronary heart disease tended to be higher among men above the median at first examination in relative weight, body fatness, systolic and diastolic blood pressure, and serum cholesterol concentration but these segregations were not statistically significant except with serum cholesterol, which was associated with p < 0.001. The data for the last pre-disease year on the men who developed coronary heart disease showed a significant relationship between incidence and systolic blood pressure as well as for cholesterol. Average data over all pre-disease years showed significantly reduced risk among the men in the bottom quartile for diastolic as well as for systolic blood pressure, while the cholesterol level was significantly prognostic over the entire range of that variable. The few men who developed coronary heart disease with low cholesterol values tended to be in the top 20 per cent of the distribution of blood pressure or relative weight or both.Relative weight showed a high but still imperfect correlation with body fatness. Arterial blood pressure tended to be elevated in extremely obese or grossly overweight men. Serum cholesterol was not significantly related to any of the other variables.Men who developed coronary heart disease tended to have low values for cholesterol in the alpha-lipoprotein fraction in the serum but the ratio of cholesterol in the alpha- to the beta-lipoprotein fraction of the serum was no more prognostic than total cholesterol alone.Comparison with similar follow-up data from Framingham, Massachusetts, Albany, New York, and Chicago, show a high degree of concordance. In all series relative weight had least significance and the incidence of coronary heart disease rose continuously with the serum cholesterol level. With men classifiedaccording to pre-disease cholesterol level, about 80 per cent of the total variance in relative subsequent risk is accounted for by regression of risk on the cholesterol value raised to any power from 2 to 3 and the correlation between observed and predicted relative risk is of the order of r = 0.9.

Fiber and Pectin in the Diet and Serum Cholesterol Concentration in Man.

Summary Rigidly controlled experiments on middle-aged men subsisting on diets of natural foods with and without supplements of 15 g daily of either cellulose(fiber) or pectin failed to show any significant effect on serum cholesterol concentration from the cellulose but they did consistently show an effect from the pectin. The pectin effect was apparent in 3 weeks and amounted to an average fall of about 5% below the level on the same diet without pectin supplement. It is suggested that the amounts of cellulose and pectin used correspond to the upper levels of these substances provided in natural human diets.

Effect of dietary fat on the fecal excretion of cholesterol and its degradation products in man

Fecal bile acid and neutral sterol excretion rates were determined in five healthy young men when serum cholesterol changes were induced by isocaloric substitution of an unsaturated (safflower oil) for a saturated fat (butter). The isotope balance method was used after the intravenous injection of cholesterol-4-(14)C. A feces extraction method is presented which permits essentially complete separation of fecal neutral sterols and bile acids. There was a significant increase in the total excretion of the fecal end products of cholesterol metabolism from 966 +/- 42 mg/day on saturated fat to 1147 +/- 45 mg/day on unsaturated fat, and the increase was equally distributed between the neutral sterol and bile acid fractions. With the substitution of dietary fats, regardless of the sequence of their feeding, there was a 28% reduction in serum cholesterol concentration during ingestion of the unsaturated fat. There were reciprocal changes in serum cholesterol levels and fecal steroid excretion with the substitution of one type of fat for the other. The changes in plasma cholesterol content were more than adequately balanced by the reciprocal changes in fecal cholesterol end product excretion. The findings in this study agree with several previous reports in supporting the hypothesis that the hypocholesteremic action of dietary unsaturated fatty acids is associated with an increase in the fecal loss of bile acids and neutral sterols.

Serum cholesterol response to changes in the diet: III. Differences among individuals

Data from 227 men in 10 sets of controlled dietary experiments in 5 institutions gave the least-squares solution: [see text] with S.E. of slope --±0.44, where X is the serum cholesterol level of an individual, X is the average for all men on the same diet, and Δ is the response to a given dietary change. Equations, a chart and a table are provided for the prediction of the serum cholesterol response when change is made from one diet to another when cholesterol and fatty acid compositions of the diets are known. Comparison of predicted with observed average values in recently published data on samples of free-living people changing diets on prescription designed to lower serum cholesterol gave, predicted versus observed Δ: −30.0 vs. −28.5 and −27.2 vs. -30.1 mg./l00 ml. in men and women in caloric balance. In a sample of men who were also losing weight on a low-fat, low-cholesterol diet a change of −33.5 was predicted versus −39.8 observed.The series of metabolic ward experiments, with 22 physically healthy men in each, covered dietary cholesterol intakes from 50 to 1450 mg. daily, with all other variables controlled. The serum-cholesterol data, plus the data from comparable experiments reported from 4 other institutions, were analyzed in regard to average serum cholesterol response (Δ Chol., mg./100 ml.) to changed cholesterol intake. Least-squares solution, using serum cholesterol responses in 19 sets of dietary cholesterol comparisons, gives Δ Chol. = 1.5(Z2 − Z1), where the subscripts refer to the diets compared and Z is the square-root of the dietary cholesterol, measured as mg./1000 Cal. The correlation between the average Δ Chol. predicted and that observed is r = 0.95. The serum response was the same over a wide range of dietary fat composition. Ordinary American diets range from about about 150 to 350 mg. cholesterol/1000 Cal. These extremes correspond to an average difference of about 9 mg. of cholesterol/100 ml. of serum if all other variables are constant. Change from 250 mg./l000 Cal. to a cholesterol-free diet will cause an average fall of about 24 mg./100 ml. of serum. But a 50 per cent decrease in dietary cholesterol will produce an average decrease in the serum of only about 7 mg./100 ml. For the purpose of controlling the serum level, dietary cholesterol should not be completely ignored but attention to this factor alone accomplishes little.

The effects of exercise and weight loss on plasma lipids in young obese men

We studied the independent and combined effects of exercise training and weight loss on blood lipids under fixed diet and exercise conditions. Twenty-one obese sedentary men were randomly allocated to one of four treatment groups: (1) inactive and constant weight (control), (2) exercise training and constant weight, (3) inactive and weight loss, and (4) exercise training and weight loss. There were three study periods: a 3 week baseline period inactive and on an isocaloric diet, a 12 week treatment period, and a 3 week weight stabilization period. Exercise consisted of treadmill walking at an energy cost of 3500 kcal/wk for groups 2 and 4 with replacement caloric intake only in group 2. Group 3 reduced caloric intake by 3500 kcal/wk during the treatment period. Weight loss for groups 3 and 4 were 13.4 pounds and 13.7 pounds, respectively. Maximal oxygen uptake (mL/min) increased 6% in both exercise groups (2 and 4), and percent body fat decreased only in these groups. Regression analysis by group assignment on HDL cholesterol (HDL-C) showed that the inactivity-weight loss modality (group 3) and the exercise-constant weight modality (group 2) each significantly increased HDL-C, with an additive effect of exercise and weight loss (group 4). The rate of HDL-C change differed significantly between groups (P = 0.01). HDL-C increased 0.63, 0.61, and 1.89 mg/dL per 3 weeks or 2%, 2.4%, and 5.5% above baseline levels in groups 2, 3, and 4, respectively, while the control group decreased 0.11 mg/dL. Plasma triglycerides and very low-density lipoprotein (VLDL) cholesterol increased with exercise at constant weight (group 2) and decreased with exercise associated with weight loss (group 4). In conclusion, exercise and weight loss separately and independently increase HDL-C, and their effects are additive.

Serum cholesterol in man: diet fat and intrinsic responsiveness.

Data obtained from a number of dietary experiments in man yield a formula by which the responses in serum cholesterol to changes in diet can be predicted. In this paper the reliability of this formula is tested and the effects of various types of fatty acids on serum cholesterol are investigated.