Substitution of dietary monounsaturated fatty acids for saturated fatty acids in a free-living population: a feasibility study

The fatty acid composition of the diet of seven free-living subjects (five men and two women) aged 41–56 years was altered for 1 month. The aim was to increase the intake of monounsaturated fatty acids (MUFAs) from subjects current habitual levels of 12% dietary energy to a target intake of 18% dietary energy, and to decrease saturated fatty acid (SFA) from habitual levels of 16% dietary energy to target levels of 10% dietary energy. The change in fatty acid intake was achieved by supplying volunteers with foods prepared using MUFA-containing spreads or olive oil (ready meals, sweet biscuits and cakes) and also by supplying spreads, cooking oil and MUFA-enriched milk for domestic use. Body weight and plasma total cholesterol measurements were made at baseline and at 2 and 4 weeks on the diet as an aid to maintaining subject compliance. MUFA consumption was significantly increased from 12% dietary energy to 16% dietary energy ( P <0.01), and SFA intake was reduced from 16% dietary energy to 6% dietary energy ( P <0.01) during the 4-week intervention. The diet failed to achieve the target increase in MUFA but exceeded the target reduction in SFA. This was due to the fact that subjects reduced their total fat intake from a mean habitual level of 38% dietary energy to a mean level of 30% dietary energy. During the dietary period, mean plasma cholesterol levels were lower at 2 weeks ( P <0.01) and at 4 weeks ( P <0.01) than the baseline, with a mean reduction of 20% over the dietary period. This study demonstrates the difficulty of achieving increased MUFA intakes (by SFA substitution) in free-living populations when only a limited range of fatty-acid modified food products are provided to volunteers.     

A lower proportion of dietary saturated/monounsaturated/polyunsaturated fatty acids reduces the expression of adiponectin in rats fed a high-fat diet

The role for the amount of different dietary fatty acids in regulating expression of adiponectin and metabolism of glucose and lipids has been implicated, but the optimal amount has not been established yet. To address this issue, we fed male Wistar rats with either chow diet or various high-fat diets (HFDs) for 12 weeks. The HFDs contained the same percentage of fat (35% energy from fat) but had different proportions of saturated/monounsaturated/polyunsaturated (S/M/P) (1:1.7:1.2, 1:1:1, 2:1.5:1, 1:2:1, or 1:1:2) fat. Glucose and lipid metabolism and adiponectin expression were subsequently examined. In comparison with chow diet, HFD with any proportion of S/M/P increased energy intake but had no obvious effect on body weight gain. The HFD with the S/M/P proportion at 1:1:1 or 1:1:2 significantly decreased the serum triglyceride level and increased the serum level of high-density lipoprotein cholesterol in comparison with the HFD with the S/M/P proportion at 1:1.7:1.2, 2:1.5:1, or 1:2:1. The HFD containing the highest level of saturated fatty acids (S/M/P proportion at 2:1.5:1) increased levels of total cholesterol, low-density lipoprotein cholesterol, and blood glucose. Levels of serum insulin and the homeostasis model assessment of insulin resistance index were significantly increased by HFD with S/M/P proportions at 1:1.7:1.2, 1:1:1, 2:1.5:1, or 1:2:1 but not by the HFD with the S/M/P proportions at 1:1:2 (containing the highest level of polyunsaturated fatty acids). Levels of adiponectin messenger RNA in subcutaneous and visceral adipose tissues were reduced by the HFD with the S/M/P proportion at 1:1.7:1.2 or 1:1:1 but increased by the HFD with the S/M/P proportion at 1:1:2. These changes in expression of adiponectin were inversely associated with those in levels of triglyceride, insulin, and homeostasis model assessment of insulin resistance. Together, the proportion of different fatty acids in diets plays an important role in expression of adiponectin and metabolism of glucose and lipids. Specifically, the proportion of S/M/P at 1:1:2 can promote expression of adiponectin, improve metabolism of glucose and lipids, and increase insulin sensitivity.     

Trans monounsaturated fatty acids and saturated fatty acids have similar effects on postprandial flow-mediated vasodilation

OBJECTIVE: Several studies suggest that a fatty meal impairs flow-mediated vasodilation (FMD), a measure of endothelial function. We tested whether the impairment was greater for trans fats than for saturated fats. We did this because we previously showed that replacement of saturated fats by trans fats in a controlled diet decreased FMD after 4 weeks. DESIGN: We fed 21 healthy men two different test meals with 0.9-1.0 g fat/kg body weight in random order: one rich in saturated fatty acids (Sat), mainly from palm kernel fat, and one rich in trans fatty acids (Trans) from partially hydrogenated soy bean oil. The study was performed in our metabolic ward. We had complete data for both diets of 21 men. RESULTS: FMD increased from a fasting value of 2.3+/-2.0% of the baseline diameter to 3.0+/-1.7% after the Sat test meal (95% CI for change -0.33, 1.70) and from 2.7+/-2.3 to 3.1+/-2.0% after the Trans test meal (95% CI for change -0.57, 1.29). The increase after the Sat meal was 0.22 (-1.18-1.61) FMD% higher than after the Trans meal. Serum triacylglycerols increased by 0.46+/-0.36 mmol/l after the Sat test meal and by 0.68+/-0.59 mmol/l after the Trans test meal; a difference of 0.23 (0.07, 0.39) mmol/l. Serum HDL-cholesterol was hardly affected by the test meals. The activity of serum paraoxonase, an esterase bound to HDL, increased slightly after the two test meals but the difference between meals was not significant. CONCLUSION: FMD was not impaired and not different after test meals with saturated or trans fatty acids. Thus, differences in long-term effects of these fats are not caused by differences in acute effects on the vascular wall.     

Effects of dietary saturated, monounsaturated, and n-3 fatty acids on blood pressure in healthy subjects

BACKGROUND: The quantity and quality of fats consumed in the diet influence the risk of cardiovascular disease (CVD). Although the effect of diet on plasma lipids and lipoproteins is well documented, less information exists on the role of fats on blood pressure (BP). OBJECTIVE: The objective was to evaluate the effects of different types of dietary fat on BP in healthy subjects. DESIGN: Healthy subjects (n = 162) were randomly assigned for 3 mo to follow 1 of 2 isoenergetic diets: 1 rich in monounsaturated fatty acids (MUFA diet) and the other rich in saturated fatty acids (SFA diet). Each group was further randomly assigned to receive supplementation with fish oil (3.6 g n-3 fatty acids/d) or placebo. RESULTS: Systolic BP (SBP) and diastolic BP (DBP) decreased with the MUFA diet [-2.2% (P = 0.009) and -3.8% (P = 0.0001), respectively] but did not change with the SFA diet [-1.0% (P = 0.2084) and -1.1% (P = 0.2116)]. The MUFA diet caused a significantly lower DBP than did the SFA diet (P = 0.0475). Interestingly, the favorable effects of MUFA on DBP disappeared at a total fat intake above the median (>37% of energy). The addition of n-3 fatty acids influenced neither SBP nor DBP. CONCLUSIONS: Changing the proportions of dietary fat by decreasing SFAs and increasing MUFAs decreased diastolic BP. Interestingly, the beneficial effect on BP induced by fat quality was negated by the consumption of a high total fat intake. The addition of n-3 fatty acids to the diet had no significant effect on BP.     

Breast milk and adipose tissue fatty acid composition in relation to maternal dietary intake

The fatty acid (FA) relative concentration (g/100g) of human milk triglyceride (TG) was compared to that of adipose tissue (AT). A high concentration of linoleic acid (C-18:2) was present in AT, probably reflecting long term high linoleic acid dietary intake. Linoleic acid was slightly lower in colostrum and transitional milk. No difference in C-18:2 relative concentration was seen between AT and human milk obtained 6 weeks post-partum. Marked short-term dietary modification in linoleic acid intake of the mother, 6 weeks post-partum, did not result in changes in C-18:2 relative concentration of human milk. In spite of measured marked intradiurnal variability in C-18:2 intake, human milk TG FA relative concentration remained remarkably constant. It is suggested that human milk TG FA composition reflects, mainly, the composition of AT. With the increased dietary intake of polyunsaturated fat in many populations, high levels of linoleic acid in human milk are to be expected. The intake of this fatty acid may exceed the suggested daily allowance and thus cause harmful effects, particularly in preterm infants.     

Effects of different ratios of monounsaturated and polyunsaturated fatty acids to saturated fatty acids on regulating body fat deposition in hamsters

ObjectiveEffects of monounsaturated fatty acid (MUFA) and polyunsaturated fatty acid consumption on regulating body fat accumulation and body weight gain are controversial between animal and human studies.MethodsWe designed a 2 × 2 factorial study, with two levels of MUFAs (60% and 30%) and two levels of polyunsaturated-to-saturated fatty acid (P/S) ratio (5 and 3) to prepare four kinds of experimental oils consisting of 60% MUFAs with a high or low P/S ratio (HMHR or HMLR, respectively) or 30% MUFAs with a high or low P/S ratio (LMHR or LMLR, respectively). Thirty-two male golden Syrian hamsters were randomly divided into four groups and fed the experimental diets containing 15% (w/w) fat for 12 wk.ResultsNo difference was observed in the mean daily food intake. Hamsters fed the LMLR diet had increased weight gain, epididymal and retroperitoneal white adipose tissues, plasma non-esterified fatty acids, insulin, hepatic acetyl coenzyme A carboxylase and malic enzyme activities, and mRNA expressions of peroxisome proliferator-activated receptor-α and sterol regulatory element-binding protein-1c among all groups (P < 0.05). Hamsters fed the HMHR diet had lower plasma insulin levels and hepatic acetyl coenzyme A carboxylase activities among groups (P < 0.05) and elevated hepatic acyl coenzyme A oxidase and carnitine palmitoyltransferase-I activities compared with those fed the LMLR diet (P < 0.05).ConclusionHamsters fed the LMLR diet had increased weight gain and body fat accumulation, whereas the HMHR diet appeared to be beneficial in preventing white adipose tissue accumulation by decreasing plasma insulin levels and increasing hepatic lipolytic enzyme activities involved in β-oxidation.     

Effects of dietary n-3 polyunsaturated fatty acids, breed and dietary vitamin E on the fatty acids of lamb muscle, liver and adipose tissue

The effect of feeding n-3 PUFA on the fatty acid composition of muscle, adipose tissue and liver of lambs was investigated. Groups of eight ram lambs per breed, SuffolkxLleyn (24 kg live weight) and Scottish Blackface (18 kg live weight), were each fed one of six diets containing one of three fat sources (50 g fatty acids/kg DM; Megalac((R)) (calcium soap of palm fatty acid distillate; Volac Ltd, Royston, Herts., UK) and formaldehyde-treated whole linseed (Trouw Nutrition UK, Northwich, Ches., UK) either alone or with fish oil (1:1, w/w) and either 100 or 500 mg alpha-tocopheryl acetate/kg DM. Feed was offered ad libitum until slaughter at approximately half breed mature live weight. The type of dietary fat had no effect on intake, growth rate or feed conversion ratio. The 3.0-fold higher concentration of 18 : 3n-3 in the linseed compared with the Megalac((R)) diet approximately doubled (P<0.001) the concentration in the neutral and polar lipid fractions of musculus semimembranosus and liver, and in adipose tissue it increased 2.5-fold. Feeding protected linseed also increased (P<0.001) concentrations of 20 : 5n-3 and 22 : 5n-3 in muscle polar lipids and both lipid fractions of liver. The linseed-fish oil raised the 20 : 5n-3 concentrations above those for the linseed diet and also increased 22 : 6n-3. Scottish Blackface lambs had lower concentrations of 18 : 3n-3 in all lipids compared with Suffolk x Lleyn lambs, but more 20 : 5n-3 in the polar lipids of muscle and liver. High levels of dietary vitamin E were associated with small decreases in the concentration of monounsaturated fatty acids and increases in PUFA. Linseed raised the PUFA : saturated fatty acid ratios in liver and adipose tissue but not in muscle, and improved the n-6 : n-3 fatty acid ratio, as did the linseed-fish oil. Different combinations of dietary fatty acids and better protection against rumen biohydrogenation are required to improve muscle PUFA : saturated fatty acids ratios.     

Effect of dietary monounsaturated fatty acids on plasma lipoproteins and apolipoproteins in women.

To determine the effects of dietary fat saturation on plasma lipoproteins, we studied 21 free-living normolipidemic women (13 pre- and 8 postmenopausal) on three consecutive diet periods. During the first 4 wk they consumed a saturated diet rich in palm oil and butter [19% saturated fatty acids (S), 14% monounsaturated fatty acids (M), and 3.5% polyunsaturated fatty acids (P)], followed by 6 wk of a monounsaturated diet rich in olive oil (11% S, 22% M, and 3.6% P), and 6 wk of a polyunsaturated diet rich in sunflower oil (10.7% S, 12.5% M, and 12.8% P). Compared with the diet rich in saturated fatty acids, both diets rich in unsaturated fatty acids had similar lowering effects on total and low-density-lipoprotein cholesterol. High-density lipoprotein cholesterol and apolipoprotein A-I were higher in the monounsaturated-rich period than in the polyunsaturated-rich (10.5% and 12.7% respectively, P less than 0.001) and the saturated-rich period (5.3%, and 7.9%, respectively, P less than 0.05). These effects were independent of menopause status. Our data show that at this level of fat intake (36% as calories), a monounsaturated-rich diet results in a less atherogenic lipid profile than either polyunsaturated- or saturated-rich diets.     

Effects of dietary essential fatty acids on active thermogenin content in rat brown adipose tissue

Rats were fed diets providing either 0.3% (low EFA), 3% (control) or 10% (high EFA) of the energy as essential fatty acids. (All diets provided 20 energy percent of fat.) Both the experimental groups had a lower body weight than the controls. Small differences were found between the groups in many traditional parameters of brown adipose tissue activity (wet weight, protein content, mitochondrial content, cytochrome c oxidase activity). A specific increase in the mitochondrial concentration of the 32,000-dalton GDP-binding protein thermogenin was observed in the high EFA group (from 0.30 to 0.45 nmol/mg). When the thermogenin content of the animal was expressed per gram body weight, the content was more than doubled (from 22 to 47 pmol/g body weight) in the high EFA group, but was unaltered in the low EFA group. It is concluded that the effect of low EFA is nonspecific and due to a general decrease in health status. The effects of high EFA are, however, specific and resemble the changes observed in animals exhibiting diet-induced thermogenesis. It is suggested that the animals fed high amounts of essential fatty acids are in a state of decreased metabolic efficiency and this may be at least in part an explanation for their low body weight.     

Dietary supplementation of high levels of saturated and monounsaturated fatty acids to ewes during late gestation reduces thermogenesis in newborn lambs by depressing fatty acid oxidation in perirenal brown adipose tissue

We hypothesized that dietary supplementation of (n-6) plus (n-3) PUFA during late gestation would increase uncoupling protein-1 (UCP1) gene expression and thereby increase thermogenic capacity of newborn lambs. Thirty twin-bearing ewes were fed rumen-protected fat (2, 4, or 8%) high in saturated and monounsaturated fatty acids (SMFA) or high in (n-6) and (n-3) PUFA. Lambs (n = 7-10 per ewe treatment group) were placed in a cold chamber at 0 degrees C for 2 h. Rectal temperature was higher at birth and increased more with cold exposure in lambs from ewes fed 2 or 4% supplemental fat than in lambs from ewes fed 8% SMFA (fat type x fat level interaction, P = 0.001). Cytochrome c oxidase activity was greatest in brown adipose tissue (BAT) lambs from ewes fed 2% SMFA or 4% PUFA (fat type x fat level interaction, P = 0.01). BAT of lambs from ewes fed 2 or 4% PUFA had nearly 7-fold more (P = 0.05) UCP1 mRNA than BAT of lambs from ewes fed 8% PUFA. UCP1 expression decreased by over 80% by 24 h of age. Supplementation of 8% fat tended to depress palmitate esterification into lipids (P = 0.07) and decreased palmitate oxidation (P = 0.003) in lamb BAT in vitro, especially in those lambs from ewes fed 8% SMFA. Thus, supplementing the diets of ewes with 8% SMFA depressed cold tolerance in newborn lambs, which was reflected in their decreased ability to oxidize fatty acids in vitro.     

Reversal of the arrhythmogenic effects of long-term saturated fatty acid intake by dietary n-3 and n-6 polyunsaturated fatty acids

This study investigated whether the adverse influences of dietary saturated animal fatty acids (SF) on vulnerability to cardiac arrhythmias in rats could be modified by crossover in maturity to diets rich in polyunsaturated fatty acids (PUFAs). The arrhythmia model was coronary artery occlusion and reperfusion under anesthesia. Animals were fed commercial stock diet (4% fat wt:wt) supplemented (12% wt:wt) with fat (final diets, 35% energy as fat). Of rats fed the SF diet for 9 and 18 mo, ventricular fibrillation (VF) occurred in 71% during occlusion and in 86% on reperfusion. Mortality from VF was 0% after 9 mo on the SF diet but 67% after 18 mo. Dietary crossover to n-3 (tuna-fish oil) or n-6 (sunflower-seed oil) PUFA-supplemented diets at 9 mo reduced arrhythmias (VF incidence less than 30% in occlusion and reperfusion) and mortality (0%). The n-3 PUFAs were most effective. Dietary interventions can be effective even when introduced in mature, high-risk animals and may be of benefit in reducing risk of sudden cardiac death.     

Effect of dietary saturated fatty acids on hormone-sensitive lipolysis in rat adipocytes

The objective of this work was to examine the mechanism by which dietary saturated fatty acids, as compared with polyunsaturated fatty acids, lower hormone-sensitive lipolysis in rat adipocytes. Rats were fed a purified diet containing 14% of a fat with a high concentration of either saturated fatty acids (coconut oil or beef fat) or polyunsaturated fatty acids (safflower oil) as a control. In addition, each diet contained 2% corn oil. The animals were fed these diets for 4 wk. Norepinephrine-stimulated lipolysis was 50% lower when diets rich in saturated fatty acids, regardless of their chain length, were fed than when a diet containing a high concentration of polyunsaturated fatty acids was fed. The specific activities of adenylate cyclase, 3',5'-cyclic nucleotide (cAMP) phosphodiesterase and hormone-sensitive lipase were lower when saturated fatty acids were fed than when polyunsaturated fatty acids were fed. Accumulation of cAMP upon stimulation with 10(-5) M norepinephrine was lower when saturated fatty acids were fed than when polyunsaturated fatty acids were fed. Moreover, adipocytes were larger when saturated fatty acids were fed than when polyunsaturated fatty acids were fed. The data obtained suggest that dietary saturated fats exert their inhibitory effect on hormone-stimulated lipolysis by influencing several points in the lipolytic cascade.     

Hepatic fatty acids and acyl desaturases in rats: effects of dietary carbohydrate and essential fatty acids

For a 9-week period, six groups of weanling male rats were fed either a fat-free diet or a diet containing 10% hydrogenated coconut oil (HCO) or 10% safflower oil (SAF), respectively. Each of these diets contained either glucose or sucrose as the only carbohydrate. In the fat-free diets, the carbohydrate level was 67.3% and in the fat-supplemented diets 44.8%. Including HCO in the fat-free diet did not significantly alter hepatic 5-, 6-, and 9-desaturase activity, whereas addition of SAF significantly depressed all these activities. As compared to glucose, sucrose induced higher 9-desaturase activity in the rats on the fat-free diets. Adding HCO or SAF to the diet, simultaneously with lowering the carbohydrate level, diminished the stimulatory effect of dietary sucrose versus glucose on 9-desaturase activity. Levels of 20:4n6 and 20:3n9 in the fatty acid profiles of the liver microsomes were not influenced by dietary carbohydrate source, neither were the activities of the 5- and 6-desaturases, providing indirect evidence that dietary sucrose, as compared to glucose, did not differently affect biosynthesis of 20:4n6 and 20:3n9.     

蔗糖聚酯对人体膳食能量摄入的影响

摘要:目的　研究油脂替代物蔗糖聚酯对人体膳食能量摄入的影响。方法　采用随机双盲交叉设计,63名志愿者分别食用3组实验蛋糕,使蔗糖聚酯的摄入量分别为0 g/d、11 g/d、22 g/d,每组蛋糕实验期1 d,间隔3 d,填写24 h膳食记录表。结果　日常膳食、摄入蔗糖聚酯0 g/d、11 g/d和22 g/d的能量摄入分别为（8 672.82±2 679.66）kJ、（9 507.35±2 343.46）kJ、（8 558.45±2 241.44）kJ和（8 390.95±2 319.36）kJ,脂肪供能比分别为（36.09±9.79）%、（37.41±6.13）%、（32.72±6.73）%和（29.63±7.73）%,摄入蔗糖聚酯较摄入普通脂肪的膳食总能量减少,脂肪供能比减少,且存在剂量反应关系。结论　蔗糖聚酯与普通脂肪相比,能降低膳食总能量摄入和脂肪供能比,可作为一种良好的油脂替代物得到广泛的应用。     

Differential effects of saturated and monounsaturated fatty acids on postprandial lipemia and incretin responses in healthy subjects.

BACKGROUND: Elevations of postprandial triacylglycerol-rich plasma lipoproteins and suppressions of HDL-cholesterol concentrations are considered potentially atherogenic. Long-term studies have shown beneficial effects of monounsaturated fatty acids (eg, oleic acid) on fasting lipid and lipoprotein concentrations in humans. A direct stimulatory effect of oleic acid on the secretion of glucagon-like peptide 1 (GLP-1) was shown in animal studies. OBJECTIVE: We compared the postprandial responses of glucose, insulin, fatty acids, triacylglycerol, gastric inhibitory polypeptide (GIP), and GLP-1 to test meals rich in saturated and monounsaturated fatty acids. DESIGN: Ten young, lean, healthy persons ingested 3 meals: an energy-free soup consumed with 50 g carbohydrate (control meal), the control meal plus 100 g butter, and the control meal plus 80 g olive oil. Triacylglycerol and retinyl palmitate responses were measured in total plasma, in a chylomicron-rich fraction, and in a chylomicron-poor fraction. RESULTS: No significant differences in glucose, insulin, or fatty acid responses to the 2 fat-rich meals were seen. Plasma triacylglycerol responses were highest after the butter meal, with chylomicron triacylglycerol rising 2.5-5-fold. Retinyl palmitate responses were higher and more prolonged after the butter meal than after the control and olive oil meals, whereas both postprandial HDL-cholesterol concentrations and GLP-1 and GIP responses were higher after the olive oil meal than after the butter meal. CONCLUSIONS: Olive oil induced lower triacylglycerol concentrations and higher HDL-cholesterol concentrations than butter, without eliciting differences in concentrations of glucose, insulin, or fatty acids. Furthermore, olive oil induced higher concentrations of GLP-1 and GIP than did butter, which may point to a relation between fatty acid composition, incretin responses, and triacylglycerol metabolism in the postprandial phase.     

Validation of a short questionnaire to qualitatively assess the intake of total fat, saturated, monounsaturated, polyunsaturated fatty acids, and cholesterol

Background To validate a self‐administered 20‐item short questionnaire (SQ) for classifying individuals according to their intake of total fat, saturated (SFA), monounsaturated (MUFA), and polyunsaturated fatty acids (PUFA), as well as cholesterol. Methods The SQ was sent to a randomly selected subsample of 300 participants of the European Prospective Investigation into Cancer and Nutrition (EPIC) in Heidelberg. The SQ was sent back by 244 participants (52.5% women, 47.5% men). Intake of total fat, SFA, MUFA, PUFA, and cholesterol was calculated from a 148‐item food frequency questionnaire (FFQ). The intake was compared with the scores computed from the SQ. Results Spearman's correlation coefficient between the intake estimated from the FFQ and the score from the SQ ranged from r = 0.29 (PUFA) to r = 0.56 (cholesterol). When the participants were assigned to quartiles of intake according to both methods 29–42% were classified into the same quartile, 1–7% of the participants were grossly misclassified. Conclusions The SQ demonstrated a good validity with respect to SFA and cholesterol and an acceptable validity with respect to total fat and MUFA, while the results are less good for PUFA. The SQ can be used to classify persons according to their intake into categories of intake.     

Modifications induced by dietary lipid source in adipose tissue phospholipid fatty acids and their consequences in lipid mobilization

The aim of the present work was to assess the influence of dietary lipid source on fatty acid phospholipid profiles and on lipid mobilization. Forty male Wistar rats were divided into four groups and fed on high-fat diets which provided olive oil, sunflower oil, palm oil or beef tallow. All rats received the same amount of energy to avoid hyperphagia and differences in energy intake among groups. Phospholipid fatty acids were determined by GC. Lipolysis was stimulated in subcutaneous and perirenal isolated adipocytes by several lipolytic agents, and assessed by the determination of released glycerol. After 4 weeks of feeding, differences in body and adipose tissue weights were not observed. Dietary regimens caused great changes in adipose tissue phospholipid composition: rats fed on palm oil and beef tallow had higher concentrations of saturated fatty acids and animals fed on olive oil or sunflower oil had greater amounts of oleic and linoleic acids, respectively. These modifications did not lead to important changes in adipocyte lipolysis. Significant differences were only observed between palm-oil- and beef-tallow-fed groups when lipolysis was stimulated by isoproterenol in subcutaneous adipocytes. The fact that our feeding protocol did not induce differences in fat accumulation among groups avoids misinterpretations due to adiposity changes. The differences observed between both saturated-fat-fed groups, therefore, should only be attributable to dietary lipids. Despite this effect, the data from this work indicate that some diet-induced changes in adipose tissue fatty acid composition may have little effect on overall function.