Body-weight regulation: causes of obesity

Diferential gene expression and adiposity reduction induced by ascorbic acid supplementation in a cafeteria model of obesity

Obesity is considered as an inflammatory disease, in which free radical-induced oxidative stress and excessive intake of macronutrients exacerbate their symptoms. In this context, we assessed in rats the possible preventive effect of the supplementation with an antioxidant molecule, ascorbic acid, in order to reduce the adiposity induced by the intake of a high-fat diet. For this purpose, during 56 days, three groups of male Wistar rats were fed on: a) standard pelleted diet, b) Cafeteria diet, c) ascorbate-supplemented (750 mg/kg of body weight) Cafeteria diet. At the end of the experimental period, microarray analysis was used to identify genes transcriptionally induced or repressed by both experimental dietary models (Cafeteria diet supplemented or not with ascorbic acid) in subcutaneous adipose tissue. Dietary ascorbic acid was able to protect against high fat diet effects, reducing the increase of body weight, total body fat and enlargement of different adipose depots induced by the Cafeteria diet without affecting food intake. An association analysis accurately and differentially allowed the detection of gene expression changes related with adiposity and insulin resistance. The genes that more strongly correlated with body fat and HOMA insulin resistance index were involved in adipocyte differentiation, lipid and glucocorticoid metabolism, cell cycle regulation, as well as in several insulin-induced processes. Some other transcripts are regulated by the vitamin C-mediated reduction of adiposity, such as genes that participate in glucocorticoid metabolism, adipogenesis, pentose phosphate pathway, or tricarboxylic acid cycle. This strategy was able to link variations in adipose tissue gene expression with markers of diet-induced obesity in rats, such as insulin resistance and body fat content.

Genes, lifestyles and obesity

OBJECTIVE

To review the role of genes and lifestyle factors, particularly dietary habits and physical activity patterns, in obesity risk as well as their potential interactions.

DESIGN AND MEASUREMENTS

A descriptive report of a number of genes definitely ascribed or potentially implicated in excessive fat accumulation leading to obesity as assessed by different research approaches (Mendelian transmission, genetic animal models, epidemiological association/linkage studies and genome-wide scans). Also, the involvement of macronutrient intake and composition (fat/carbohydrate) as well as the role of activity-linked energy expenditure in obesity onset is reviewed.

RESULTS

Examples of the role of the genotype as well as of the dietary macronutrient composition/intake and sedentary/low energy cost of physical activities in obesity prevalence are reported.

CONCLUSIONS

Both genes and everyday life environmental factors such as cultural and social mediated food intake and reduced domestic and living work activities are involved in the obesity pandemia. The occurrence of gene x gene and gene x environmental factors interactions makes it more difficult to interpret the specific roles of genetics and lifestyle in obesity risk.

Effects of dietary fat and energy on body weight and composition after gonadectomy in cats

OBJECTIVE

To evaluate the effect of dietary fat and energy density on body weight gain, body composition, and total energy expenditure (TEE) in neutered and sexually intact cats.

ANIMALS

12 male and 12 female cats

PROCEDURE

Male cats were castrated (castrated male [CM]) or underwent no surgical procedure (sexually intact male [IM]). Female cats underwent ovariectomy (spayed female [SF]) or laparotomy and ligation of both uterine tubes without ovary removal (sexually intact female [IF]). Cats were fed either the low-fat (LF) or high-fat (HF) diet for 26 weeks, with the final allocation consisting of 8 groups: IF-LF IF-HE SF-LF, SF-HF IM-LF, IM-HF, CM-LF, and CM-HF. Mean food intake for each group was recorded daily, and body weight was monitored weekly throughout the study. Body composition and TEE were measured before surgery in week 0 and at the end of the study (week 26) by isotope dilution (double-labelled water).

RESULTS

N eutered cats gained significantly more body fat and body weight (53.80+/-5.79%) than sexually intact cats (27.11+/-5.79%) during the study. Body weight gain of neutered cats fed the HF diet was greater than those fed the LF diet. Following correction for body composition, TEE was similar in all groups and no pattern towards increased food intake was evident.

CONCLUSIONS AND CLINICAL RELEVANCE

Weight gain in neutered cats was decreased by feeding an LF, low energy-dense diet. To prevent weight gain in cats after neutering, a suitable LF diet should be fed in carefully controlled meals rather than ad libitum.

Genetic manipulation in nutrition, metabolism, and obesity research

We summarize the current standard methods for overexpressing, inactivating, or manipulating genes, with special focus on nutritional and obesity research. These molecular biology procedures can be carried out with the maintenance of the genetic information to subsequent generations (transgenic technology) or devised to exclusively transfer the genetic material to a given target animal, which cannot be transmitted to the future progeny (gene therapy). On the other hand, the RNA interference (RNAi) approach allows for the creation of new experimental models by transient ablation of gene expression by degrading specific mRNA, which can be applied to assess different biological functions and mechanisms. The combination of these technologies contributes to the study of the function and regulation of different metabolism- and obesity-related genes as well as the identification of new pharmacologic targets for nutritional and therapeutic approaches.

Prevalence and trends in overweight in Mexican-american adults and children

Overweight and obesity have been increasing in many countries. Our objective is to describe the trends in overweight and obesity occurring in the Mexican-American population in the United States. Data on measured height and weight for Mexican Americans come from the following surveys: the Hispanic Health and Nutrition Examination Survey (HHANES, 1982-84), the Third National Health and Nutrition Examination Survey (NHANES III, 1988-94), and NHANES 1999-2002. In 1999-2002, 73% of Mexican-American adults were overweight and 33% were obese. Obesity increased between NHANES III and NHANES 1999-2002, from 24% to 27% for men and from 35% to 38% for women. Increases were also seen for children and adolescents. The Mexican-American population in the United States, both children and adults, is showing trends in overweight and obesity over time that are similar to those seen in other segments of the U.S. population and indeed in many countries.

Basal and postprandial substrate oxidation rates in obese women receiving two test meals with different protein content

BACKGROUND & AIMS

Fuel utilisation and storage in lean and obese subjects seem to be differently affected by the macronutrient distribution intake. The aim of this intervention study was to explore the extent to which the fat mass status and the macronutrient composition of an acute dietary intake influence substrate oxidation rates.

METHODS

Fuel utilisation in 26 women, 14 obese (BMI = 37.1 +/- 1.1 kg/m2) and 12 lean (BMI = 20.6 +/- 0.5 kg/m2) was measured over 6 h to compare the metabolic effect of a single balanced protein (HC) meal and a high protein (HP) single meal, which were designed to supply similar energy contents (1672 kJ). The macronutrient composition as a percentage of energy of the HC meal was 55% carbohydrate, 15% protein and 30% fat, while the HP meal contained 40% carbohydrate, 30% protein and 30% fat. Nutrient oxidation rates and energy expenditure were calculated by indirect calorimetry (hood system), whereas exogenous amino acid oxidation was estimated from the 13C isotopic enrichment of breath after oral administration of L[1-13C]leucine.

RESULTS

Fasting lipid oxidation was higher in the obese than in the lean women (P < 0.05), and it was significantly correlated with body fatness (P < 0.01). A single HP meal consumption produced higher postprandial fat oxidation as compared with HC meal intake (P < 0.02), in both obese and lean subjects, with no apparent changes in glucose oxidation rates. Furthermore, postprandial fat utilisation after the test meal intake was higher in obese than in the lean women (P < 0.01). The time course of 13CO2 in breath followed a similar pattern in both dietary groups, although a non-statistically significant higher trend in protein and 13C-leucine oxidation was found in the HP group.

CONCLUSIONS

Net lipid oxidation depends on both short-term dietary composition intake and fat body mass, being significantly higher after a relatively high protein meal as compared to a balanced diet intake and in obese women as compared to lean controls.

Public health nutrition and genetics: implications for nutrition policy and promotion

The unravelling of the human genome has the potential to radically extend many of the strategies used in public health nutrition to improve health and to increase food availability, accessibility and utilization. The present paper divides nutrigenomics into two broad but differing areas in asking about possible public health applications: (1) the increasing mismatch between population growth and global food security, on top of the already approximately 800 million of the world population who are food insecure; (2) possible responses to the rising prevalence of non-communicable diseases as the Western diet becomes increasingly inappropriate to the needs of those consuming it. It is clear that complex interactions of multiple polymorphisms play a role in how individuals and sub-populations respond to dietary interventions. All these applications present public health and ethical challenges, particularly in ensuring that any benefits that do come from nutrigenomics are not restricted to the wealthy minority of only the affluent nations. The present paper concludes that the public health applications of nutrigenomics are probably at least a decade away, especially for developing countries. Clinical applications are likely to be more immediate, probably resulting in 'designer diets' for individuals with particular polymorphisms, but unless governments take on the role of ensuring some extent of equity in access, any benefits are most likely to go to those who can afford the screening, tests and treatment. At the same time, greatly increased international efforts are needed towards the continuing, and in some cases worsening, global malnutrition, as genetic manipulation of crops is unlikely to provide more than part of the solution.

Physiological and metabolic functions of melatonin

Melatonin is a lipophilic hormone, mainly produced and secreted at night by the pineal gland. Melatonin synthesis is under the control of postganglionic sympathetic fibers that innervates the pineal gland. Melatonin acts via high affinity G protein-coupled membrane receptors. To date, three different receptor subtypes have been identified in mammals: MT1 (Mel 1a) and MT2 (Mel 1b) and a putative binding site called MT3. The chronobiotic properties of the hormone for resynchronization of sleep and circadian rhythms disturbances has been demonstrated both in animal models or in clinical trials. Several other physiological effects of melatonin in different peripheral tissues have been described in the past years. In this way, it has been demonstrated that the hormone is involved in the regulation of seasonal reproduction, body weight and energy balance. This contribution has been focused to review some of the physiological functions of melatonin as well as the role of the hormone in the regulation of energy balance and its possible involvement in the development of obesity.

A cross-national comparison of lifestyle between China and the United States, using a comprehensive cross-national measurement tool of the healthfulness of lifestyles: the Lifestyle Index

BACKGROUND

Extensive studies have revealed the importance of a healthy lifestyle and the role of each lifestyle factor in health. However, lifestyle factors have rarely been studied simultaneously. The authors propose an integrated approach to summarize total healthfulness of lifestyles and to enhance understanding of lifestyle patterns across countries.

METHODS

The authors created an overall measure of lifestyle called the Lifestyle Index (LI), integrating diet, physical activity, smoking, and alcohol use to provide a global tool of monitoring healthfulness and patterns of lifestyles. Using the LI, the authors conducted a cross-national comparison between China (n = 8352) and the United States (n = 9750).

RESULTS

The LI effectively reflected the healthfulness of lifestyle components in both countries. The mean of the LI scores was slightly higher in China than the US. Scores of diet quality, physical activity, and smoking were higher in China, but scores of alcohol behavior were higher in the US. Similar lifestyle patterns but different unhealthy behaviors were identified in these countries.

CONCLUSIONS

An assessment of total healthfulness of lifestyles and a better understanding of lifestyle patterns across countries using the LI can provide practical guidance to developing and targeting public health promotion activities to improve global public health.

Obesity risk is associated with carbohydrate intake in women carrying the Gln27Glu beta2-adrenoceptor polymorphism

Interindividual differences in the response to dietary intake are, in some cases, genotype dependent. Moreover, genotype-environment interactions may appear when the impact of lifestyle factors (e.g., diet) on a phenotype (e.g., BMI > 30 kg/m(2)) differs by genotype. A case-control study (obese subjects vs. normal weight controls) was conducted to assess a possible effect modification on obesity risk of the Gln27Glu polymorphism for the beta(2)-adrenoceptor gene depending on dietary intake. The sample included 159 subjects with BMI > 30 kg/m(2) and 154 controls with BMI < 25 kg/m(2). The allele frequency for the Glu27 polymorphism, as assessed by the polymerase chain reaction-restriction fragment length polymorphism methodology, was 0.40 in cases (obese) and 0.37 in controls (lean), which was similar to that of other Caucasian populations. The dietary intake was estimated by using a previously validated food frequency questionnaire. Obesity incidence was not directly affected by the polymorphism [odds ratio (OR) = 1.40; P = 0.246]. However, a significant interaction (effect modification) between carbohydrate (CHO) intake and the presence of the Glu27 variant in the probability of obesity was apparent. Thus, females with the polymorphism and a higher CHO intake [>49% energy (E)] had a higher obesity risk (OR = 2.56, P = 0.051). The product-term introduced in the logistic model to assess effect modification revealed a marginally significant interaction (P = 0.058) between both factors. Furthermore, a high intake of CHO (E > 49%) was associated with higher insulin levels among women carrying the Gln27Glu polymorphism (P < 0.01). This gene-nutrient interaction emphasizes the importance of examining the outcome of some obesity-related mutations depending on lifestyle (including diet) and may explain the heterogeneity of findings from previous studies.

In vivo assessment of the mitochondrial response to caloric restriction in obese women by the 2-keto[1-C]isocaproate breath test

The 2-keto[1-(13)C]isocaproate breath test has been proposed as a tool to detect mitochondrial dysfunction in alcoholic liver disease. The aim of this study was to evaluate if the 2-keto[1-(13)C]isocaproate breath test could detect in vivo dynamic changes on mitochondrial activity due to caloric restriction in obese women. Fifteen obese women (body mass index [BMI] > 30 kg/m(2)) participated in the study at baseline. Ten of these women agreed to participate on a diet program to induce body weight loss. Fifteen lean women (BMI < 25 kg/m(2)) were included as a control group. The breath test was performed by the oral administration of the tracer measuring (13)CO(2) enrichment in breath before and after ingestion using isotope ratio mass spectrometry. Body composition, resting energy expenditure, and plasma levels of insulin and leptin were measured. There were no relationships observed between the 2-keto[1-(13)C]isocaproate breath test and the plasma insulin (before diet: P =.863; after diet: P =.879), or leptin (before diet: P =.500; after diet: P =.637). In obese women before treatment, kilograms of fat free mass (P =.108), resting energy expenditure adjusted for body composition (P =.312), and the 2-keto[1-(13)C]isocaproate breath test (P =.205) were similar in comparison to lean women. However, 2-keto[1-(13)C]isocaproate oxidation tended to increase after dieting and was significantly higher than in controls (P =.015). These data suggest that the 2-keto[1-(13)C]isocaproate breath test reflected the adaptive modifications in mitochondrial oxidation in response to caloric restriction in obese women.

AH. Obesidade: hábitos nutricionais, sedentarismo e resistência à insulina

A obesidade já é considerada uma epidemia mundial independente de condições econômicas e sociais. O risco aumentado de mortalidade e morbidade associado à obesidade tem sido alvo de muitos estudos que tentam elucidar os aspectos da síndrome X como conseqüência da obesidade. Esta síndrome é caracterizada por algumas doenças metabólicas, como resistência à insulina, hipertensão, dislipidemia. Está bem estabelecido que fatores genéticos têm influência neste aumento dos casos de obesidade. No entanto, o aumento significativo nos casos de obesidade nos últimos 20 anos dificilmente poderia ser explicado por mudanças genéticas que tenham ocorrido neste espaço de tempo. Sendo assim, os principais fatores envolvidos no desenvolvimento da obesidade têm sido relacionados com fatores ambientais, como ingestão alimentar inadequada e redução no gasto calórico diário. Na tentativa de desencadear obesidade em animais e permitir o estudo desta doença de maneira mais completa, diversos modelos experimentais de obesidade têm sido desenvolvidos. Ainda que não possam ser considerados exatamente iguais aos modelos de obesidade humana, são de grande valor no estudo dos diversos aspectos que contribuem para este excessivo acúmulo de adiposidade e suas conseqüências.

Familial clustering of obesity and the role of nutrition: Tehran Lipid and Glucose Study

OBJECTIVE

To clarify the hypothesis that parent's dietary intakes are associated with their offspring's body mass index.

DESIGN

Observational analytical cross-sectional survey among inhabitants of district 13 in the east of Tehran.

SUBJECTS

A total of 117 healthy families comprising 474 subjects including 240 offspring (3-25 y old).

MEASUREMENTS

Weight and height were measured by a standard protocol and body mass index (kg/m(2)) was calculated. Dietary intakes were assessed by means of a 2 day dietary recall questionnaire.

RESULTS

The prevalence of overweight was 11.8% in offspring of normal-weight parents, 19.0% in offspring of overweight fathers and normal-weight mothers, 25.4% in offspring of overweight mothers and normal-weight fathers and 40.8% in offspring with both parents overweight. The Offspring's overweight was significantly and independently associated with high-energy intake of both parents (odds ratio; 95% CI 2.7; 1.6-4.5). Adjusted for the sex of parents, the chances of offspring being overweight were higher in overweight (3.8; 1.5-9.2) and high-energy-intake mothers (2.6; 1.2-5.6) and high-energy-intake fathers (2.0; 1.1-3.9) as compared with children of normal-weight parents. High fat intake of husbands was an independent risk factor increasing the chances of their wives being overweight (2.1; 1.5-3.6) and vice versa (1.8; 1.2-2.8).

CONCLUSION

The observed familial obesity pattern was shown to be associated with the familial dietary intakes. Hence, familial intervention seems essential to stop the accelerated rise in the prevalence of overweight and obesity in our community.

Strategies for the Management of Patients with Obesity

The prevalence of overweight and obesity is increasing worldwide. During the last two decades, the prevalence of adults in the higher body mass index (BMI) categories in the US has increased the most, as much as 300% for those with a BMI above 40kg/m2. In children and adolescents, a doubling of the prevalence of severe overweight poses a serious health risk to future generations of young adults who may develop chronic diseases normally associated with aging. The simple definition of obesity, an imbalance between energy intake and energy expenditure, ignores the complexity of, and largely unknown interactions between, genes, food intake and physical activity, which together determine bodyweight and fat distribution. Although the etiology and manifestations of overweight and obesity are complex, the assessment of overweight and obesity requires only an accurate measurement of bodyweight, height and abdominal circumference, as well as a history and physical examination attuned to the morbidities that commonly accompany overweight and obesity such as diabetes mellitus, hypertension, dyslipidemia and sleep apnea. The treatment of patients with overweight and obesity continues to be based on changes to diet and physical activity. Simple behavior modification techniques are within the reach of busy clinicians. The additional use of available bodyweight reduction medications can reliably lead to a 5 to 10% reduction from initial bodyweight, a loss that has been shown to provide significant health benefit. The use of meal replacements has also been shown to be effective and is probably an under-appreciated treatment resource. Surgery is the most successful treatment for those with severe obesity and should be discussed as an option for those in the appropriate bodyweight categories. Because societal trends favor the greater intake of calorie-dense foods and less physical activity to accomplish the activities of daily life, the future of obesity treatment will require the development of bodyweight reduction medications that work by a variety of mechanisms to decrease food intake or increase energy expenditure. Such medications should not be viewed as a 'crutch' but rather as a 'helping hand' that enable people to better adhere to a healthier lifestyle.