Peter D. Wood

Changes in plasma lipids and lipoproteins in overweight men during weight loss through dieting as compared with exercise.

We studied separately the influence of two methods for losing fat weight on the levels of plasma lipids and lipoproteins in overweight sedentary men--decreasing energy intake without increasing exercise (diet), and increasing energy expenditure without altering energy intake (exercise, primarily running)--in a one-year randomized controlled trial. As compared with controls (n = 42), dieters (n = 42) had significant loss of total body weight (-7.8 +/- 0.9 kg [mean +/- SE]), fat weight (-5.6 +/- 0.8 kg), and lean (non-fat) weight (-2.1 +/- 0.5 kg) (P less than 0.001 for each variable), and exercisers (n = 47) had significant loss of total body weight (-4.6 +/- 0.8 kg) and fat weight (-3.8 +/- 0.7 kg) (P less than 0.001 for both variables) but not lean weight (-0.7 +/- 0.4 kg). Fat-weight loss did not differ significantly between dieters and exercisers. All subjects were discouraged from altering their diet composition; however, dieters and exercisers had slight reductions in the percentage of kilojoules derived from fat. As compared with the control group, both weight-loss groups had significant increases (P less than 0.01) in plasma concentrations of high-density lipoprotein (HDL) cholesterol (diet vs. exercise, 0.13 +/- 0.03 vs. 0.12 +/- 0.03 mmol per liter), HDL2 cholesterol (0.07 +/- 0.02 vs. 0.07 +/- 0.02 mmol per liter), and HDL3 cholesterol (0.07 +/- 0.02 vs. 0.06 +/- 0.02 mmol per liter) and significant decreases (P less than 0.05) in triglyceride levels (diet vs. exercise, -0.35 +/- 0.14 vs. -0.24 +/- 0.12 mmol per liter). Levels of total and low-density lipoprotein cholesterol were not significantly changed, relative to values in controls. None of these changes were significantly different between dieters and exercisers. Thus, we conclude that fat loss through dieting or exercising produces comparable and favorable changes in plasma lipoprotein concentrations.

Effects of Diet and Exercise in Men and Postmenopausal Women with Low Levels of HDL Cholesterol and High Levels of LDL Cholesterol

BACKGROUND Guidelines established by the National Cholesterol Education Program (NCEP) promote exercise and weight loss for the treatment of abnormal lipoprotein levels. Little is known, however, about the effects of exercise or the NCEP diet, which is moderately low in fat and cholesterol, in persons with lipoprotein levels that place them at high risk for coronary heart disease. METHODS We studied plasma lipoprotein levels in 180 postmenopausal women, 45 through 64 years of age, and 197 men, 30 through 64 years of age, who had low high-density lipoprotein (HDL) cholesterol levels (< or =59 mg per deciliter in women and < or =44 mg per deciliter in men) and moderately elevated levels of low-density lipoprotein (LDL) cholesterol (>125 mg per deciliter but <210 mg per deciliter in women and >125 mg per deciliter but <190 mg per deciliter in men). The subjects were randomly assigned to aerobic exercise, the NCEP Step 2 diet, or diet plus exercise, or to a control group, which received no intervention. RESULTS Dietary intake of fat and cholesterol decreased during the one-year study (P<0.001), as did body weight, in women and men in either the diet group or the diet-plus-exercise group, as compared with the controls (P<0.001) and the exercise group (P<0.05), in which dietary intake and body weight were unchanged. Changes in HDL cholesterol and triglyceride levels and the ratio of total to HDL cholesterol did not differ significantly among the treatment groups, for subjects of either sex. The serum level of LDL cholesterol was significantly reduced among women (a decrease of 14.5+/-22.2 mg per deciliter) and men (a decrease of 20.0+/-17.3 mg per deciliter) in the diet-plus-exercise group, as compared with the control group (women had a decrease of 2.5+/-16.6 mg per deciliter, P<0.05; men had a decrease of 4.6+/-21.1 mg per deciliter, P<0.001). The reduction in LDL cholesterol in men in the diet-plus-exercise group was also significant as compared with that among the men in the exercise group (3.6+/-18.8 mg per deciliter, P<0.001). In contrast, changes in LDL cholesterol levels were not significant among the women (a decrease of 7.3+/-18.9 mg per deciliter) or the men (10.8+/-18.8 mg per deciliter) in the diet group, as compared with the controls. CONCLUSIONS The NCEP Step 2 diet failed to lower LDL cholesterol levels in men or women with high-risk lipoprotein levels who did not engage in aerobic exercise. This finding highlights the importance of physical activity in the treatment of elevated LDL cholesterol levels.

The Effects on Plasma Lipoproteins of a Prudent Weight-Reducing Diet, with or without Exercise, in Overweight Men and Women

Abstract Background. The National Cholesterol Education Program (NCEP) recommends a low-saturated-fat, low-cholesterol diet, with weight loss if indicated, to correct elevated plasma cholesterol levels. Weight loss accomplished by simple caloric restriction or increased exercise typically increases the level of high-density lipoprotein (HDL) cholesterol. Little is known about the effects on plasma lipoproteins of a hypocaloric NCEP diet with or without exercise in overweight people. Methods. We tested the hypothesis that exercise (walking or jogging) will increase HDL cholesterol levels in moderately overweight, sedentary people who adopt a hypocaloric NCEP diet. We randomly assigned 132 men and 132 women 25 to 49 years old to one of three groups: control, hypocaloric NCEP diet, or hypocaloric NCEP diet with exercise. One hundred nineteen of the men and 112 of the women returned for testing after one year. Results. After one year, the subjects in both intervention groups had reached or closely approached ...

Variations in oxidative susceptibility among six low density lipoprotein subfractions of differing density and particle size

Oxidative modification of low density lipoproteins (LDL) has been implicated in the sequence of events leading to fatty streak formation in the arterial intima. Increased oxidative modifications of dense versus buoyant LDL particles could contribute to increased atherosclerosis associated with lipoprotein profiles enriched in small, dense LDL. In the present studies, we compared rates of copper-induced oxidative changes for six LDL subfractions ranging in density from 1.023 to 1.053 g/ml and mean particle diameter from 282 +/- 10 to 245 +/- 3. Rates of formation of thiobarbituric acid-reactive substances (TBARS), as indicated by the time required for half-maximal TBARS formation (T1/2max), decreased with increasing density and decreasing particle diameter to a minimum in fraction 5 (d = 1.046 g/ml, diameter = 250 +/- 5) (P = 0.007). In parallel studies using unfractionated LDL (d = 1.019-1.063 g/ml), T1/2max values were inversely correlated with the predominant LDL species diameter as determined by 2-16% gradient gel electrophoresis (P less than 0.05), consistent with the involvement of subclass composition in determining oxidative behavior. In separate experiments, subfraction differences in oxidation rates as assessed by TBARS formation were verified by the finding of similarly dispartate changes in fluorescence intensity and anionic electrophoretic mobility. T1/2max values were not related to LDL contents of alpha-tocopherol, beta-carotene, protein, triglycerides or phospholipids, but were significantly correlated with unesterified cholesterol content (r = 0.46; P less than 0.001) and were inversely associated with cholesteryl ester content (r = 0.28; P less than 0.05). The positive association of T1/2max with unesterified cholesterol suggests that this constituent may impart resistance to oxidative modification, possibly by altering properties of the surface monolayer where it resides.

Increased exercise level and plasma lipoprotein concentrations: A one-year, randomized, controlled study in sedentary, middle-aged men☆

Eighty-one sedentary but healthy men aged 30-55 participated in a 1 yr randomized study of the effects of exercise on plasma lipoprotein concentrations. Forty-eight were assigned to a running program, while 33 remained as sedentary controls (an approximately 3:2 ratio). After 1 yr the running group had become significantly fitter and leaner than the control group. Lipoprotein concentration changes in the runners (vs. controls) uniformly favored reduced risk of coronary heart disease, but were not significant when all 46 participants with complete data were included. However, the 25 men who averaged at least eight miles (12.9 kilometers) per wk of running increased their plasma high-density-lipoprotein (HDL) cholesterol level by 4.4 mg/dl (p = 0.045) and their HDL2 mass level by 33 mg/dl (p = 0.059), vs. controls. Significant correlations were found for distance run per wk vs. change in plasma HDL-cholesterol (r = 0.48), HDL2 (r = 0.41), and low-density-lipoprotein cholesterol (r = -0.31). Changes in percent body fat and in HDL-cholesterol were correlated (r = -0.47) in runners. There appears to be a threshold at about 8 miles per wk above which a 1-yr running program leads to beneficial lipoprotein changes.

The distribution of plasma lipoproteins in middle-aged male runners*†

Stimulated by increasing evidence of an inverse relationship between plasma high-density lipoprotein cholesterol level and frequency of coronary heart disease, we determined concentrations of fasting plasma cholesterol, triglyceride, and lipoproteins in 41 very active men (running greater than 15 miles/wk for the previous year) 35-59 years of age (mean age, 47) and in a comparison group of men of similar age, randomly selected from three northern California communities. The runners had significantly (p less than 0.05) decreased mean plasma triglyceride (70 versus 146 mg/100 ml), total plasma cholesterol (200 versus 210 mg/100 ml), and low-density lipoprotein (LDL) cholesterol (125 versus 139 mg/100 ml) concentrations, and a higher mean level of high-density lipoprotein (HDL) cholesterol (64 versus 43 mg/100 ml) than the comparison group (n equals 147 for HDL and LDL; n equals 743 for total cholesterol and triglycerides). These very active men exhibited a plasma lipoprotein profile resembling that of younger women rather tan of sedentary, middle-aged men. This characteristic, and apparently advantageous, pattern could be only partially accounted for by differences in adiposity between runners and control subjects.

The effect of exercise on plasma high density lipoproteins

The influence of vigorous activity in man on plasma lipids and lipoproteins is reviewed, with particular emphasis on high density lipoproteins. Both cross sectional and longitudinal (or training) studies have been reported, many of them of less than ideal design. Nonetheless, a consistent pattern emerges in which increased exercise levels lead to lower plasma concentrations of triglycerides and very low density lipoproteins, and of low density lipoproteins. High density lipoprotein levels increase. Sometimes, but not uniformly, plasma total cholesterol level falls as the result of these changes. The increase in plasma high density lipoprotein appears to be the result largely of an increase in the less dense HDL2 subfraction. Plasma apolipoprotein A-I levels (but not apo-A-II levels) seem to increase concomitantly. The precise biochemical mechanism responsible for these changes has not been elucidated; but the recent finding of increased lipoprotein lipase activity in adipose tissue and muscle of endurance runners suggests that increased lipolytic rate of trigly ceride-rich lipoproteins may be an initial step in a sequence of events leading to higher plasma levels of HDL2.

Effect of Postmenopausal Hormone Therapy on Lipoprotein(a) Concentration

BACKGROUND Postmenopausal hormone therapy has been reported to decrease levels of lipoprotein (Lp)(a) in cross-sectional studies and small or short-term longitudinal studies. We report findings from a large, prospective, placebo-controlled clinical trial that allows a broad characterization of these effects for four regimens of hormone therapy. METHODS AND RESULT The Postmenopausal Estrogen/Progestin Interventions study was a 3-year, placebo-controlled, randomized clinical trial to assess the effect of hormone regimens on cardiovascular disease risk factors in postmenopausal women 45 to 65 years of age. The active regimens were conjugated equine estrogens therapy at 0.625 mg daily, alone or in combination with each of three regimens of progestational agents: medroxyprogesterone acetate (MPA) at 2.5 mg daily (ie, continuous MPA), MPA at 10 mg days 1 to 12 (ie, cyclical MPA), and micronized progesterone at 200 mg days 1 to 12. Plasma levels of Lp(a) were measured at baseline (n = 366), 12 months (n = 354), and 36 months (n = 342). Assignment to hormone therapy resulted in a 17% to 23% average drop in Lp(a) concentrations relative to placebo (P<.0001), which was maintained across 3 years of follow-up. No significant differences were observed among the four active arms. Changes in Lp(a) associated with hormone therapy were positively correlated with changes in LDL cholesterol, total cholesterol, apolipoprotein B, and fibrinogen levels and were similar across subgroups defined by age, weight, ethnicity, and prior hormone use. CONCLUSIONS Postmenopausal estrogen therapy, with or without concomitant progestin regimens, produces consistent and sustained reductions in plasma Lp(a) concentrations.

An in vitro study of anterior cruciate ligament graft placement and isometry

Isometric positioning of the ACL graft or prosthesis is an important consideration in successful reconstruction of the ACL-deficient knee. This study documented the relationship between graft placement and intraarticular graft length changes and graft tension changes during knee passive range of motion. Fifteen fresh cadaveric knees were mounted in sta bilizing rigs. The ACL was identified and cut in each specimen. Intraarticular reconstruction was then per formed using a 6 mm polypropylene braid (3M LAD, St. Paul, MN). The following graft placements were evalu ated : 1) over-the-top, 2) modified over-the-top with a femoral bone trough, 3) femoral drill hole positions, and 4) tibial drill hole positions. The proximal end of the graft was fixed to the lateral aspect of the femur with a screw and spiked washer. The distal end of the graft was attached to a turnbuckle attached to a load cell on the anterior aspect of the tibia. The knee was then extended passively from 90° to 0°. Two experiments were performed. In Experiment A, the turnbuckle was adjusted to keep graft tension constant and the graft length changes were recorded. In Experiment B, the graft fixation sites were not altered and tension changes with range of motion were recorded. A change in the graft distance between attachment sites with knee range of motion can be monitored either by ligament length or by tension change. With the over- the-top technique, in Experiment A, the graft distance between attachment sites increased as the knee was extended (x = 4.9 mm); in Experiment B, large tension increases were recorded with knee extension. With the modified over-the-top technique with femoral bone trough, isometry was approached as the average length increase with knee extension was reduced to 1.0 mm (Experiment A) and minimal tension increases occurred (Experiment B). Femoral drill holes positioned postero superiorly on the lateral femoral condyle produced vari able length or tension increases with knee extension. Anteriorly positioned femoral drill holes produced sig nificant length decreases with knee extension in Exper iment A (x = -5.5 mm) while tension measurements showed loss of graft tension with knee extension (Ex periment B). Finally, tibial drill hole position was also found to be vital for proper isometric tracking. Tibial drill holes situated immediately anterior to the antero medial portion of the ACL insertional site yielded the best isometric placement for the femoral orientations tested. Care must be taken, however, that this tibial position does not cause impingement in the intercon dylar notch.

Contributions of regional adipose tissue depots to plasma lipoprotein concentrations in overweight men and women: Possible protective effects of thigh fat☆

Anthropometry and dual-photon absorptiometry (DPA) were used to examine associations of regional adiposity with plasma lipid, lipoprotein, and lipoprotein subfraction mass concentrations in moderately overweight men and women. Among 130 women, waist to thigh girth ratio (WTR) correlated with triglycerides (TG) (r = .33, P less than .0001) and negatively with high-density lipoprotein (HDL)-cholesterol (HDL-C) (r = -.37, P less than .0001) concentration, as expected. While WTR did not correlate with low-density lipoprotein (LDL)-cholesterol (LDL-C) it correlated positively with the mass subfraction of small (Sfo, 0 to 7) LDL (r = .38, P less than .0001), and negatively with large (Sfo, 7 to 12) LDL (r = -.31, P less than .01). Among 133 men, similar though weaker relationships were found. Thigh girth correlated positively with HDL and HDL2-C and mass, and with LDL particle size among women. Multivariate analysis suggests that association of WTR with lipoprotein values known to carry risk of coronary heart disease (CHD) are due at least as much to effects of thigh girth as to deleterious effects of waist girth. Estimates of fat weight in thigh and abdominal regions by DPA support thigh fat as contributing to these effects of thigh girth. Thigh fat may contribute to lipoprotein profiles that predict lower risk of cardiovascular disease.