Dietary Fat Intake, Supplements, and Weight Loss

2000 ◽  
Vol 25 (6) ◽  
pp. 495-523 ◽  
Author(s):  
David J. Dyck
Keyword(s):  
Weight Loss ◽  
Linoleic Acid ◽  
Conjugated Linoleic Acid ◽  
Dietary Fat ◽  
Fat Oxidation ◽  
Fat Content ◽  
High Fat ◽  
Underlying Assumption ◽  
High Fat Diets ◽  
Fat Diets

Although there remains controversy regarding the role of macronutrient balance in the etiology of obesity, the consumption of high-fat diets appears to be strongly implicated in its development. Evidence that fat oxidation does not adjust rapidly to acute increases in dietary fat, as well as a decreased capacity to oxidize fat in the postprandial state in the obese, suggest that diets high in fat may lead to the accumulation of fat stores. Novel data is also presented suggesting that in rodents, high-fat diets may lead to the development of leptin resistance in skeletal muscle and subsequent accumulations of muscle triacylglycerol. Nevertheless, several current fad diets recommend drastically reduced carbohydrate intake, with a concurrent increase in fat content. Such recommendations are based on the underlying assumption that by reducing circulating insulin levels, lipolysis and lipid oxidation will be enhanced and fat storage reduced. Numerous supplements are purported to increase fat oxidation (carnitine, conjugated linoleic acid), increase metabolic rate (ephedrine, pyruvate), or inhibit hepatic lipogenesis (hydroxycitrate). All of these compounds are currently marketed in supplemental form to increase weight loss, but few have actually been shown to be effective in scientific studies. To date, there is little or no evidence supporting that carnitine or hydroxycitrate supplementation are of any value for weight loss in humans. Supplements such as pyruvate have been shown to be effective at high dosages, but there is little mechanistic information to explain its purported effect or data to indicate its effectiveness at lower dosages. Conjugated linoleic acid has been shown to stimulate fat utilization and decrease body fat content in mice but has not been tested in humans. The effects of ephedrine, in conjunction with methylxanthines and aspirin, in humans appears unequivocal but includes various cardiovascular side effects. None of these compounds have been tested for their effectiveness or safety over prolonged periods of time. Key words: carnitine, conjugated linoleic acid, ephedrine, pyruvate, hydroxycitrate

scholarly journals Effects of dietary fat and conjugated linoleic acid on plasma metabolite concentrations and metabolic responses to homeostatic signals in pigs

2002 ◽  
Vol 88 (6) ◽  
pp. 625-634 ◽  
Author(s):  
E. Ostrowska ◽  
R. F. Cross ◽  
M. Muralitharan ◽  
D. E. Bauman ◽  
F. R. Dunshea
Keyword(s):  
Linoleic Acid ◽  
Conjugated Linoleic Acid ◽  
Plasma Glucose ◽  
Dietary Fat ◽  
De Novo ◽  
Lipid Synthesis ◽  
High Fat ◽  
Triacylglycerol Synthesis ◽  
High Fat Diets ◽  
Fat Diets

Sixteen female cross-bred (Large White × Landrace) pigs (initial weight 65 kg) with venous catheters were randomly allocated to four treatment groups in a 2×2 factorial design. The respective factors were dietary fat (25 or 100 g/kg) and dietary conjugated linoleic acid (CLA; 0 or 10 g CLA-55/kg). Pigs were fed every 3 h (close to ad libitum digestible energy intake) for 8 d and were bled frequently. Plasma glucose and non-esterified fatty acid (NEFA) responses to insulin and adrenaline challenges were determined on day 8. Plasma concentrations of NEFA were significantly increased (10·5 and 5·4 % for low- and high-fat diets respectively, P=0·015) throughout the experiment, suggesting that there was a possible increase in fat mobilisation. The increase in lipolysis, an indicator of ß-adrenergic stimulated lipolysis, was also evident in the NEFA response to adrenaline. However, the increase in plasma triacylglycerol (11·0 and 7·1 % for low- and high-fat diets respectively, P=0·008) indicated that CLA could have reduced fat accretion via decreased adipose tissue triacylglycerol synthesis from preformed fatty acids, possibly through reduced lipoprotein lipase activity. Plasma glucose, the primary substrate for de novo lipid synthesis, and plasma insulin levels were unaffected by dietary CLA suggesting that de novo lipid synthesis was largely unaffected (P=0·24 and P=0·30 respectively). In addition, the dietary CLA had no effect upon the ability of insulin to stimulate glucose removal.

scholarly journals The role of high-fat diets and physical activity in the regulation of body weight

2000 ◽  
Vol 84 (4) ◽  
pp. 417-427 ◽  
Author(s):  
Patrick Schrauwen ◽  
Klaas R. Westerterp
Keyword(s):  
Physical Activity ◽  
Dietary Fat ◽  
High Fat Diet ◽  
Fat Oxidation ◽  
Fat Intake ◽  
High Fat ◽  
High Fat Diets ◽  
Prevalence Of Obesity ◽  
Fat Diets

The prevalence of obesity is increasing in westernized societies. In the USA the age-adjusted prevalence of BMI ≫30 kg/m2 increased between 1960 and 1994 from 13 % to 23 % for people over 20 years of age. This increase in the prevalence of obesity has been attributed to an increased fat intake and a decreased physical activity. However, the role of the impact of the level of dietary fat intake on human obesity has been challenged. High-fat diets, due to their high energy density, stimulate voluntary energy intake. An increased fat intake does not stimulate its own oxidation but the fat is stored in the human body. When diet composition is isoenergetically switched from low to high fat, fat oxidation only slowly increases, resulting in positive fat balances on the short term. Together with a diminished fat oxidation capacity in pre-obese subjects, high-fat diets can therefore be considered to be fattening. Another environmental factor which could explain the increasing prevalence of obesity is a decrease in physical activity. The percentage of body fat is negatively associated with physical activity and exercise has pronounced effects on energy expenditure and substrate oxidation. High-intensity exercise, due to a lowering of glycogen stores, can lead to a rapid increase in fat oxidation, which could compensate for the consumption of high-fat diets in westernized societies. Although the consumption of high-fat diets and low physical activity will easily lead to the development of obesity, there is still considerable inter-individual variability in body composition in individuals on similar diets. This can be attributed to the genetic background, and some candidate genes have been discovered recently. Both leptin and uncoupling protein have been suggested to play a role in the prevention of diet-induced obesity. Indeed, leptin levels are increased on a high-fat diet but this effect can be attributed to the increased fat mass observed on the high-fat diet. No effect of a high-fat diet per se on leptin levels is observed. Uncoupling proteins are increased by high-fat diets in rats but no data are available in human subjects yet. In conclusion, the increased intake of dietary fat and a decreasing physical activity level are the most important environmental factors explaining the increased prevalence of obesity in westernized societies.

scholarly journals Macronutrient balances and obesity: the role of diet and physical activity

1999 ◽  
Vol 2 (3a) ◽  
pp. 341-347 ◽  
Author(s):  
Arne Astrup
Keyword(s):  
Physical Activity ◽  
Weight Loss ◽  
Body Weight ◽  
Weight Gain ◽  
Physical Fitness ◽  
Dietary Fat ◽  
High Fat Diet ◽  
Fat Oxidation ◽  
Fat Content ◽  
High Fat

AbstractObservational cross-sectional and longitudinal studies suggest that a high fat diet and physical inactivity are independent risk factors for weight gain and obesity. Mechanistic and intervention studies support that fat possesses a lower satiating power than carbohydrate and protein, and a diet low in fat therefore decreases energy intake. The effect of dietary fat on energy balance is enhanced in susceptible subjects, particularly in sedentary individuals with a genetic predisposition to obesity who consume a high fat diet.Dietary carbohydrate promotes its own oxidation by an insulin-mediated stimulation of glucose oxidation. In contrast, high fat meals do not increase fat oxidation acutely. A sedentary life-style and low physical fitness cause a low muscular fat oxidation capacity, and the consumption of a high fat diet by these individuals promotes fat storage in a synergistic fashion.Ad libitum low fat diets cause weight loss proportional to pre-treatment body weight in a dose-dependent way, i.e. weight loss is correlated positively to the reduction in dietary fat content. Increased physical activity prevents relapse after weight loss and studies have shown that those who keep up a higher level of physical activity are more successful in maintaining the reduced body weight. In conclusion, important interactions exist between genetic make up, dietary fat and physical fitness, so that a low fitness level and susceptible genes reduce muscular fat oxidation capacity which may decrease the tolerance of dietary fat. Increasing daily physical activity and reducing dietary fat content may be more effective when combined than when separate in preventing weight gain and obesity.

Cats increase fatty acid oxidation when isocalorically fed meat-based diets with increasing fat content

1999 ◽  
Vol 277 (3) ◽  
pp. R878-R886 ◽  
Author(s):  
Tammy Lester ◽  
Gail Czarnecki-Maulden ◽  
Douglas Lewis
Keyword(s):  
Fat Oxidation ◽  
Fat Content ◽  
Acid Oxidation ◽  
Fat Intake ◽  
High Fat ◽  
Short Term ◽  
Body Fat Content ◽  
High Fat Diets ◽  
Maintain Body Weight ◽  
Fat Diets

This study tested the hypothesis that sedentary cats have the ability to adapt to high-fat carnivore diets by increasing fat oxidation. Twenty-four hour indirect calorimetry was used to determine total energy expenditure (TEE) and macronutrient oxidation in six vasectomized male (VAS) and six ovariectomized female (OVX) cats isocalorically fed lower-fat (53% fat, 45% protein) and higher-fat (71% fat, 26% protein) meat-based diets at maintenance for 8 days. Fat oxidation increased linearly with fat intake with a mean slope of 0.91 g fat oxidized/g fat intake ( P < 0.001), with no change in TEE. However, VAS male cats were able to more precisely match fat oxidation with fat intake than OVX female cats ( P < 0.02). Body fat content did not significantly influence fat oxidation. These results demonstrate that cats maintain body weight during short-term isocaloric feeding of a high-fat carnivore-type diet in part by increasing fat oxidation commensurate with increases in fat intake. This ability may be an important mechanism underlying the resistance of cats to obesity, despite habitual consumption of high-fat diets.

Failure to increase lipid oxidation in response to increasing dietary fat content in formerly obese women

1994 ◽  
Vol 266 (4) ◽  
pp. E592-E599 ◽  
Author(s):  
A. Astrup ◽  
B. Buemann ◽  
N. J. Christensen ◽  
S. Toubro
Keyword(s):  
Dietary Fat ◽  
High Fat Diet ◽  
Matched Control ◽  
Fat Content ◽  
Carbohydrate Oxidation ◽  
Control Group ◽  
Obese Women ◽  
High Fat ◽  
High Fat Diets ◽  
Fat Diets

The effect of an increase in dietary fat content on fat and carbohydrate balances and energy expenditure (EE) was studied in nine formerly obese women with genetic predisposition to obesity (postobese) and a closely matched control group. Isocaloric low- (20% fat energy) and high-fat diets (50%) were consumed for 3 days preceding and during a 24-h respiratory chamber stay, whereas a medium-fat diet (30%) was consumed only on the day of measurement. After adjustment for 24-h energy intake to equal 24-h EE, 24-h fat balance was increased when the dietary fat content increased (P < 0.0002). No differences in macronutrient balances were found on the low-fat and medium-fat diets, but on the high-fat diet the postobese women failed to increase ratio of fat to carbohydrate oxidation appropriately (0.59 g/g, 95% confidence interval 0.47-0.67 vs. controls 1.02 g/g, 0.88–1.12; P = 0.002). This caused a positive adjusted fat balance (+11.0 g/day, 2.3–19.6 vs. controls -8.9 g/day, -17.5 to -0.2; P < 0.001) and a negative carbohydrate balance (-41.8 g/day, -69.5 to -14.0 vs. controls +23.2 g/day, -4.6 to +50.9; P < 0.001). Decreasing the dietary fat content increased 24-h EE in the postobese women (P = 0.02), whereas it was unaffected in the control group. Independent of energy balance, an increase in dietary fat content to 50% fat energy results in preferential fat storage, impaired suppression of carbohydrate oxidation, and reduction of 24-h EE in postobese women.

scholarly journals Induction of ketosis in rats fed low-carbohydrate, high-fat diets depends on the relative abundance of dietary fat and protein

2011 ◽  
Vol 300 (1) ◽  
pp. E65-E76 ◽  
Author(s):  
Maximilian Bielohuby ◽  
Dominik Menhofer ◽  
Henriette Kirchner ◽  
Barbara J. M. Stoehr ◽  
Timo D. Müller ◽  
...  
Keyword(s):  
Weight Loss ◽  
Body Weight ◽  
Dietary Fat ◽  
Peroxisome Proliferator ◽  
High Fat ◽  
Macronutrient Composition ◽  
Peroxisome Proliferator Activated Receptor ◽  
Low Carbohydrate ◽  
High Fat Diets ◽  
Fat Diets

Low-carbohydrate/high-fat diets (LC-HFDs) in rodent models have been implicated with both weight loss and as a therapeutic approach to treat neurological diseases. LC-HFDs are known to induce ketosis; however, systematic studies analyzing the impact of the macronutrient composition on ketosis induction and weight loss success are lacking. Male Wistar rats were pair-fed for 4 wk either a standard chow diet or one of three different LC-HFDs, which only differed in the relative abundance of fat and protein (percentages of fat/protein in dry matter: LC-75/10; LC-65/20; LC-55/30). We subsequently measured body composition by nuclear magnetic resonance (NMR), analyzed blood chemistry and urine acetone content, evaluated gene expression changes of key ketogenic and gluconeogenic genes, and measured energy expenditure (EE) and locomotor activity (LA) during the first 4 days and after 3 wk on the respective diets. Compared with chow, rats fed with LC-75/10, LC-65/20, and LC-55/30 gained significantly less body weight. Reductions in body weight were mainly due to lower lean body mass and paralleled by significantly increased fat mass. Levels of β-hydroxybutyate were significantly elevated feeding LC-75/10 and LC-65/20 but decreased in parallel to reductions in dietary fat. Acetone was about 16-fold higher with LC-75/10 only ( P < 0.001). In contrast, rats fed with LC-55/30 were not ketotic. Serum fibroblast growth factor-21, hepatic mRNA expression of hydroxymethylglutaryl-CoA-lyase, peroxisome proliferator-activated receptor-γ coactivator-1α, and peroxisome proliferator-activated receptor-γ coactivator-1β were increased with LC-75/10 only. Expression of phospho enolpyruvate carboxykinase and glucose-6-phosphatase was downregulated by 50–70% in LC-HF groups. Furthermore, EE and LA were significantly decreased in all groups fed with LC-HFDs after 3 wk on the diets. In rats, the absence of dietary carbohydrates per se does not induce ketosis. LC-HFDs must be high in fat, but also low in protein contents to be clearly ketogenic. Independent of the macronutrient composition, LC-HFD-induced weight loss is not due to increased EE and LA.

Non-Fasting Factor VII Coagulant Activity (FVII:C) Increased by High-Fat Diet

1994 ◽  
Vol 71 (06) ◽  
pp. 755-758 ◽  
Author(s):  
E M Bladbjerg ◽  
P Marckmann ◽  
B Sandström ◽  
J Jespersen
Keyword(s):  
High Fat Diet ◽  
Fat Content ◽  
Factor Vii ◽  
Amidolytic Activity ◽  
High Fat ◽  
Low Fat Diet ◽  
Increased Risk ◽  
Coagulant Activity ◽  
High Fat Diets ◽  
Fat Diets

SummaryPreliminary observations have suggested that non-fasting factor VII coagulant activity (FVII:C) may be related to the dietary fat content. To confirm this, we performed a randomised cross-over study. Seventeen young volunteers were served 2 controlled isoenergetic diets differing in fat content (20% or 50% of energy). The 2 diets were served on 2 consecutive days. Blood samples were collected at 8.00 h, 16.30 h and 19.30 h, and analysed for triglycerides, FVII coagulant activity using human (FVII:C) or bovine thromboplastin (FVII:Bt), and FVII amidolytic activity (FVIPAm). The ratio FVII:Bt/FVII:Am (a measure of FVII activation) increased from fasting levels on both diets, but most markedly on the high-fat diet. In contrast, FVII: Am (a measure of FVII protein) tended to decrease from fasting levels on both diets. FVII:C rose from fasting levels on the high-fat diet, but not on the low-fat diet. The findings suggest that high-fat diets increase non-fasting FVII:C, and consequently may be associated with increased risk of thrombosis.

scholarly journals Dietary linoleic acid at high and reduced dietary fat level decreases the faecal excretion of vitamin E in young rats

1997 ◽  
Vol 77 (2) ◽  
pp. 327-336 ◽  
Author(s):  
Lilian B. M. Tuburg ◽  
Edward Haddeman ◽  
Gerard A. A. Kivits ◽  
Jan A. Weststrate ◽  
Elizabeth J. Brink
Keyword(s):  
Fatty Acids ◽  
Linoleic Acid ◽  
Vitamin E ◽  
Dietary Fat ◽  
High Fat ◽  
Dietary Linoleic Acid ◽  
Dietary Pufa ◽  
Faecal Excretion ◽  
Reduced Fat ◽  
Fat Diets

Vitamin E is the major lipid-soluble antioxidant in human subjects and is crucial in protecting polyunsaturated fatty acids (PUFA) against lipid peroxidation. Dietary PUFA have been suggested to inhibit the absorption of vitamin E. The present study in young male rats was designed to investigate the effect of increasing concentrations of dietary linoleic acid on the faecal excretion of vitamin E. The rats were fed on semi-synthetic diets containing two concentrations of fat (59 g/kg diet, 15 energy % (en%) or 131 g/kg, 30 en%) for 3 weeks. Triacylglycerol rich in linoleic acid was added at the expense of triacylglycerol rich in saturated fatty acids to obtain dietary concentrations of 13,39 or 66 g linoleic acid/kg diet for the high-fat diet (131 g fat/kg) and 12, 24 or 36 g linoleic acid/kg diet for the reduced-fat diet (59 g fat/kg). The results from the present study demonstrate that the faecal excretion of vitamin E was significantly lower in rats fed on diets with high levels of linoleic acid compared with rats fed on lower levels of linoleic acid irrespective of the dietary fat content. The concentration of vitamin E in liver and plasma was significantly lower in animals fed on the highest concentration of linoleic acid compared with those fed on the lowest level. Results from the present study also demonstrate that at the same concentration of linoleic acid, the faecal excretion of vitamin E in rats fed on reduced-fat diets was significantly lower than in rats fed on high-fat diets. Our findings indicate that the apparent absorption of vitamin E is not inhibited by dietary PUFA. Results from the present study also demonstrate that a reduction of dietary fat content from 30 en% to 15 en% does not lower the apparent absorption of vitamin E

Elevated n-3 fatty acids in a high-fat diet attenuate the increase in PDH kinase activity but not PDH activity in human skeletal muscle

2005 ◽  
Vol 98 (1) ◽  
pp. 350-355 ◽  
Author(s):  
Erin A. Turvey ◽  
George J. F. Heigenhauser ◽  
Michelle Parolin ◽  
Sandra J. Peters
Keyword(s):  
Skeletal Muscle ◽  
Fatty Acids ◽  
Pyruvate Dehydrogenase ◽  
High Fat Diet ◽  
Human Skeletal Muscle ◽  
Fat Content ◽  
Pyruvate Dehydrogenase Kinase ◽  
High Fat ◽  
High Fat Diets ◽  
Fat Diets

We tested the hypothesis that a high-fat diet (75% fat; 5% carbohydrates; 20% protein), for which 15% of the fat content was substituted with n-3 fatty acids, would not exhibit the diet-induced increase in pyruvate dehydrogenase kinase (PDK) activity, which is normally observed in human skeletal muscle. The fat content was the same in both the regular high-fat diet (HF) and in the n-3-substituted diet (N3). PDK activity increased after both high-fat diets, but the increase was attenuated after the N3 diet (0.051 ± 0.007 and 0.218 ± 0.047 min−1 for pre- and post-HF, respectively; vs. 0.073 ± 0.016 and 0.133 ± 0.032 min−1 for pre- and post-N3, respectively). However, the active form of pyruvate dehydrogenase (PDHa) activity decreased to a similar extent in both conditions (0.93 ± 0.17 and 0.43 ± 0.09 mmol/kg wet wt pre- and post-HF; vs. 0.87 ± 0.19 and 0.39 ± 0.05 mmol/kg wet wt pre- and post-N3, respectively). This suggested that the difference in PDK activity did not affect PDHa activation in the basal state, and it was regulated by intramitochondrial effectors, primarily muscle pyruvate concentration. Muscle glycogen content was consistent throughout the study, before and after both diet conditions, whereas muscle glucose-6-phosphate, glycerol-3-phosphate, lactate, and pyruvate were decreased after the high-fat diets. Plasma triglycerides decreased after both high-fat diets but decreased to a greater extent after the N3, whereas plasma free fatty acids increased after both diets, but to a lesser extent after the N3. In summary, PDK activity is decreased after a high-fat diet that is rich in n-3 fatty acids, although PDHa activity was unaltered. In addition, our data demonstrated that the hypolipidemic effect of n-3 fatty acids occurs earlier (3 days) than previously reported and is evident even when the diet has 75% of its total energy derived from fat.

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