Zuheir Habbal

High protein vs high carbohydrate hypoenergetic diet for the treatment of obese hyperinsulinemic subjects.

OBJECTIVE: To test the hypothesis that hyperinsulinemic obese subjects would respond differently to changes in the composition of hypoenergetic diets.DESIGN: A 4-week randomized dietary intervention trial.SUBJECTS: Thirteen male obese hyperinsulinemic normoglycemic subjects were divided into two groups and fed hypoenergetic diets providing 80% of their resting energy expenditure (REE). One group received a high-protein diet (HP; 45% protein, 25% carbohydrates, and 30% fat as percent of dietary energy) and the other a high-carbohydrate diet (HC; 12% protein, 58% carbohydrates and 30% fat).MEASUREMENTS: Anthropometry, body composition, fasting serum insulin and lipids, and REE were performed before and after the feeding period.RESULTS: Weight loss was higher in the HP than HC group (8.3±0.7 vs 6.0±0.6 kg, P<0.05). There was a decrease in body fat in both groups, whereas body water decreased significantly more in the HP group. REE decreased more in the HC than the HP group (−384.3±84.6 vs −132.3±51.0 kcal, P<0.05). Serum total cholesterol, triglycerides and LDL cholesterol decreased significantly to a similar extent in both diet groups, while HDL cholesterol was decreased significantly only in the HP group. Mean fasting insulin decreased significantly in both diet groups and reached the normal range only in the HP group.CONCLUSION: A low-carbohydrate (LC), HP hypoenergetic diet could be the diet composition of choice for a weight-reducing regimen in obese hyperinsulinemic subjects.

Effects of dietary canola, olive, and linolenic acid enriched olive oils on plasma lipids, lipid peroxidation and lipoprotein lipase activity in rats

Abstract This study investigated the effect of α-linolenic acid enriched virgin olive, canola and virgin olive oil on body composition, serum lipids, lipid peroxidation and adipose tissue lipoprotein lipase activity in rats. Twenty six male Sprague Dawley rats were fed ad-libitum three diets, containing 40% of dietary calories from fat being either canola (CO), virgin olive (VO), or α-linolenic acid enriched virgin olive oil (LO) for seven weeks. At the end of feeding period, the rats were killed by decapitation and blood samples were analyzed for serum triglycerides (TG), total and HDL-Cholesterol (TC and HDL-C), glucose, insulin, malondialdehyde (MDA) and 4-hydroxy-2(E)-nonenal (4-HNE). Carcasses were analysed for water, fat, and protein content. Individual fat pads were dissected out and weighed. Fat cell size and number, and adipose tissue lipoprotein lipase activity were determined. Results showed that serum triglycerides levels were lower in the CO and LO as compared to VO group. Total plasma cholesterol levels were not different between the CO and LO group but were significantly lower than the VO group. The α-linolenic acid enrichment of VO seems to mimic the effect of CO on blood lipids, and hence could be responsible for reducing triglycerides and total cholesterol, and increasing HDL-C/total cholesterol ratio when compared to VO. Feeding CO, resulted in significantly lower 4-HNE levels as compared to VO and LO. The effects of α-linolenic acid may be explained by its conversion into eicosapentaenoic acid (EPA), which has been previously reported to produce the same effects on plasma lipids. Further studies are needed to elucidate other possible mechanisms of action of α-linolenic acid on the atherogenic factors.

DIFFERENTIAL EFFECTS OF DIETARY OILS ON PLASMA LIPIDS, LIPID PEROXIDATION AND ADIPOSE TISSUE LIPOPROTEIN LIPASE ACTIVITY IN RATS

The potential health benefits of various dietary oils in relation to cardiovascular disease and cancer are currently receiving considerable attention. This study investigated the effects of dietary canola, virgin olive, soybean, and sesame oils on body composition, serum lipids, lipid peroxidation and adipose tissue lipoprotein lipase activity in rats. Thirty-six male Sprague-Dawley rats were fed, ad-libitum, four diets each containing 40% of dietary energy in the form of either canola (CO), virgin olive (VO), soybean (BO), or sesame oils (SO) for seven weeks, with free access to water. At the end of the feeding period, the rats were sacrificed by decapitation and blood samples were analyzed for serum triglycerides (TG), total and HDL-Cholesterol (TC and HDL-C), glucose, insulin, malondialdehyde (MDA) and 4-hydroxy-2(E)-nonenal (4-HNE). Carcasses were analyzed for water, fat, and protein. Fat cell size and number, and adipose tissue lipoprotein lipase activity were determined from epididymal fat pads. Results showed a lower deposition of fat and lower percent liver fat in CO and BO groups as compared to SO and VO. Serum analysis also revealed a higher HDL-C/TC in CO group as compared to the other three groups. Serum triglyceride levels were highest in the VO group. SO group manifested the lowest levels of serum lipid peroxides. Lipoprotein lipase activity in adipose tissue homogenates (THATLPLA) per cell was significantly lower in VO as compared to BO and CO fed rats. It can be concluded that feeding CO resulted in a more favorable plasma lipid response than the other three vegetable oils whereas lipid oxidation was significantly lower with SO than CO feeding.

High protein vs high carbohydrate hypoenergetic diet in treatment of obese normoinsulinemic and hyperinsulinemic subjects

This study tests the hypothesis that hyperinsulinemic (HI) obese subjects respond differently from normoinsulinemics (NI) to changes in composition of hypoenergetic diets. Twenty-seven obese male subjects, 13 HI and 14 NI, were fed for 4 weeks either a high protein (HP) or a high carbohydrate (HC) hypoenergetic diet providing 80% of their resting energy expenditure (REE). On the HP diet weight loss was significantly higher in HI as compared to NI group. Alternatively, the HI group lost less weight than NI group on the HC diet. The HC diets resulted in a considerable and similar reduction in REE in both HI and NI groups as opposed to the HP diet, which maintained REE in both HI and NI. A higher decrease and normalization of fasting insulin levels was observed in the HI group on the HP as compared to HC diet. In conclusion, hyperinsulinemic, in contrast to normoinsulinemic obese subjects, seem to achieve better weight reduction, less decline in energy expenditure, and normalization of insulin levels on HP than isocaloric HC diet.

Restoration of Normal Insulinemia and Insulin Sensitivity in Hyperinsulinemic Normoglycemic Men by a Hypoenergetic High Monounsaturated Fat Diet

Purpose: To test the hypothesis that the macronutrient composition of hypoenergetic diets is an important consideration in weight-reducing regimens of hyperinsulinemic normoglycemic obese subjects. Design: A 4-week randomized dietary intervention trial. Subjects and Methods: Sixteen male obese hyperinsulinemic normoglycemic subjects were recruited and 15 completed the study. The participants were divided into two groups and fed hypoenergetic diets providing 80% of their resting energy expenditure (REE). One group received a high carbohydrate diet (HC) (60% carbohydrate, 20% fat, 20% protein as a percentage of dietary energy) and the other group received a high monounsaturated fat diet (HM) (35% carbohydrate, 45% fat and 20% protein). Anthropometry, body composition, REE, serum glucose, insulin and lipid analyses were performed before and after the feeding period. Results: The subjects on the HC diet achieved comparable weight loss but without restoration of normoinsulinemia and insulin sensitivity. Fasting insulin levels, insulin to glucose ratio, and Homeostatic Model & Assessment Index decreased to normal ranges and were significantly lower in the HM group as compared with the HC group. Similarly, insulin sensitivity score (Mffm/I) increased significantly on the HM diet. Waist circumference measurements showed a significantly higher decrease on the HM than HC diet, whereas body weight, percentage body fat, glucose, plasma lipids, and REE decreased to the same extent whether subjects were fed the HC or HM diet. Conclusions: In this study, feeding a HM diet was more effective than a HC diet for restoring normoinsulinemia and insulin sensitivity. Therefore, hyperinsulinemic normoglycemic obese subjects may benefit from a diet lower in carbohydrates and higher in monounsaturated fats for decreasing cardiovascular disease risk factors while achieving the desired weight reduction.

Diet composition affects weight gain, adiposity and blood parameters in healthy human volunteers

Thesis (M.S.)-- American University of Beirut. Department of Food Technology and Nutrition, 1997.

Cytoskeletal control of calcium absorption across the rat small intestine

1. The effect of colchicine, cytochalasin-B and procaine on calcium transport across the rat small intestine was investigated. The results obtained show the following: 2. Colchicine and cytochalasin-B at different concentrations inhibited significantly (P less than 0.001) calcium accumulation in rat intestinal cells, whereas procaine at different concentrations increased significantly (P less than 0.001) calcium accumulation in the rat small intestine. 3. Unidirectional influx of calcium across the rat small intestine was significantly inhibited (P less than 0.01) in the presence of colchicine and cytochalasin-B in the preincubation medium. Procaine, on the other hand, caused a significant increase (P less than 0.01) in the unidirectional influx of calcium across the rat intestinal cells. 4. The cell water content was not altered in the presence of the different drugs indicating that the changes in calcium transport across the rat intestinal cells are not due to alterations in the structure of the cell membrane.

Cysteamine-induced duodenal ulcer: effects on calcium absorption across rat duodenum.

The effect of cysteamine-induced duodenal ulcers on calcium transport across rat duodenum was investigated. Intracellular calcium accumulation measured after 24 hr and 3 days of cysteamine injection showed a significant increase (P less than 0.001) in the duodenal strips isolated after 3 days with no change noticed in those isolated after 24 hr, although the morphological changes in both were very similar. The relationship between increasing calcium concentration in the incubation medium and intracellular calcium concentration is a saturable process that conforms to the Michaelis-Menten type of kinetics. The average maximal flux (Vmax) increased from 8.93 nmole/hr-gdw in normal to 12.5 nmole/hr-gdw in 3-day-ulcerated rats, with no apparent change in the Michaelis constant (Kt) (0.8 mM). Unidirectional influx of calcium across the mucosal membrane was significantly increased (P less than 0.001) in 3-day-ulcerated duodenum suggesting that the increase in calcium transport could be due to the activation of the active step at the mucosal border.

Effect of different dietary saturated fats on plasma lipid levels and adipose tissue lipoprotein lipase in rats

Abstract The metabolic effects of feeding diets containing different sources of saturated fats on plasma lipid levels were studied in rats. Twenty four male Sprague Dawley rats were divided into three groups with average weight of 268.43±3.46 (g±SE). Rats were fed diets containing 50% of dietary calories from butter (B), cocoa butter (CB) and coconut oil (CO). During the last 3 days of the 7 week adlibitum feeding period fecal fat was measured. After a 12 hour fast, the rats were sacrificed and blood samples were analyzed for serum triglycerides, total and HDL cholesterol and Insulin. Samples from the right epididymal fat pad were assayed for adipose tissue Lipoprotein Lipase activity (AT-LPLA). Adipocyte size also was measured. Results showed that CO fed rats gained more weight and deposited more fat than CB or B.fed rats. Percent fat absorption was significantly lower in CB than either CO or B fed rats. Carcass analysis showed that total dissectible fat, percent body fat and adipocyte size were significantly greater in CO than CB fed rats. CO fed rats maintained higher HDL cholesterol levels than CB fed rats. AT-LPLA per fat cell did not differ between the three groups of rats. We conclude that coconut oil raises HDL-C levels when it replaces B or CB. This effect is not mediated by AT-LPLA