Mauro E. Valencia

Effects of a Traditional Lifestyle on Obesity in Pima Indians

OBJECTIVE The Pima Indians of Arizona have the highest reported prevalences of obesity and non-insulin-dependent diabetes mellitus (NIDDM). In parallel with abrupt changes in lifestyle, these prevalences in Arizona Pimas have increased to epidemic proportions during the past decades. To assess the possible impact of the environment on the prevalences of obesity and NIDDM, data were collected on members of a population of Pima ancestry (separation 700–1,000 years ago) living in a remote mountainous location in northwestern Mexico, with a lifestyle contrasting markedly with that in Arizona. RESEARCH DESIGN AND METHODS Pima heritage was established by history and by use of Pima language. Measurements of weight, height, body fat (bio-impedance), blood pressure, plasma levels of glucose, cholesterol, and HbA1c were obtained in 19 women (36 ±13 years of age) and 16 men (48 ±14 years of age) and compared with sex-, age- and diabetes status-matched Pimas living in Arizona (10 Arizona Pimas for each Mexican Pima). RESULTS Mexican Pimas were lighter (64.2 ± 13.9 vs. 90.2 ± 21.1 kg, P < 0.0001; means ± SD) and shorter (160 ± 8 vs. 164 ± 8 cm, P < 0.01) with lower body mass indexes (24.9 ± 4.0 vs. 33.4 ± 7.5 kg/m2, P < 0.0001) and lower plasma total cholesterol levels (146 ± 30 vs. 174 ± 31 mg/dl, P < 0.0001) than Arizona Pimas. Only two women (11%) and one man (6%) had NIDDM, contrasting with the expected prevalences of 37 and 54% in female and male Arizona Pimas, respectively. CONCLUSIONS This preliminary investigation shows that obesity, and perhaps NIDDM, is less prevalent among people of Pima heritage living a “traditional” lifestyle than among Pimas living in an “affluent” environment. These findings suggest that, despite a similar potential genetic predisposition to these conditions, a traditional lifestyle, characterized by a diet including less animal fat and more complex carbohydrates and by greater energy expenditure in physical labor, may protect against the development of cardiovascular disease risk factors, obesity, and NIDDM.

Effects of Traditional and Western Environments on Prevalence of Type 2 Diabetes in Pima Indians in Mexico and the U.S.

OBJECTIVE—Type 2 diabetes and obesity have genetic and environmental determinants. We studied the effects of different environments on these diseases in Pima Indians in Mexico and the U.S. RESEARCH DESIGN AND METHODS—Adult Pima-Indian and non-Pima populations in the Sierra Madre mountains of Mexico were examined using oral glucose tolerance tests and assessments for obesity, physical activity, and other risk factors. Results were compared with those from Pima Indians in Arizona. Both Pima populations were typed for DNA polymorphisms to establish their genetic similarity. RESULTS—The age- and sex-adjusted prevalence of type 2 diabetes in the Mexican Pima Indians (6.9%) was less than one-fifth that in the U.S. Pima Indians (38%) and similar to that of non-Pima Mexicans (2.6%). The prevalence of obesity was similar in the Mexican Pima Indians (7% in men and 20% in women) and non-Pima Mexicans (9% in men and 27% in women) but was much lower than in the U.S. Pima Indians. Levels of physical activity were much higher in both Mexican groups than in the U.S. Pima Indians. The two Pima groups share considerable genetic similarity relative to other Native Americans. CONCLUSIONS—The much lower prevalence of type 2 diabetes and obesity in the Pima Indians in Mexico than in the U.S. indicates that even in populations genetically prone to these conditions, their development is determined mostly by environmental circumstances, thereby suggesting that type 2 diabetes is largely preventable. This study provides compelling evidence that changes in lifestyle associated with Westernization play a major role in the global epidemic of type 2 diabetes.

Daily energy expenditure in Mexican and USA Pima Indians: low physical activity as a possible cause of obesity

BACKGROUND: Obesity is caused by an imbalance between energy intake and energy expenditure. However, it is unknown whether increased physical activity protects susceptible populations against the development of obesity and type 2 diabetes.OBJECTIVE: To investigate the potential protective role of environment and physical activity against obesity by measuring total energy expenditure in Mexican and USA Pima Indians.METHODS: We compared the physical activity level of 40 (17 female and 23 male; 37±11 y, 66±13 kg) Mexican Pima Indians from a remote, mountainous area of Northwest Mexico, with 40 age-and-sex matched (17 female and 23 male; 37±12 y, 93±22 kg) Pima Indians from the Gila River Indian Community in Arizona, USA. We measured total energy expenditure (TEE) by doubly labeled water and calculated physical activity by different methods: physical activity level (PAL) as the ratio of TEE on resting metabolic rate (RMR), TEE adjusted for RMR by linear regression, activity energy expenditure adjusted for body weight (AEE), and activity questionnaire.RESULTS: Physical activity was higher in Mexican Pima Indians when compared with USA Pima Indians as assessed by PAL (1.97±0.34 vs 1.57±0.16, P<0.0001), TEE adjusted for RMR (3289±454 vs 2671±454 kcal/day, P<0.0001) and AEE adjusted for body weight (1243±415 vs 711±415 kcal/day, P<0.0001). Questionnaires revealed more time spent on occupational activities among Mexican Pima compared with USA Pima (23.9±13.3 vs 12.6±13.9 h/week, P<0.001).CONCLUSION: These data support a significant role for physical activity in the prevention of obesity in genetically susceptible populations.

Lifestyle intervention in primary care settings improves obesity parameters among Mexican youth.

Intervention studies in youth with obesity that can be translated into primary care are limited. We compared a lifestyle intervention to a brief intervention applied by primary care physicians (control group) for treating pediatric obesity in the primary care setting. Seventy-six youth with obesity (body mass index [BMI] >95th percentile or >90th percentile plus waist circumference >90th percentile, aged 9 to 17 years) participated in a 12-month, randomized, controlled trial, conducted at a primary care unit in Northern México from June 2006 through October 2007. Participants randomized to lifestyle intervention attended a family-centered program consisting of 12 sessions of behavioral curriculum, dietary advice from a registered dietitian (weekly for the first 3 months and monthly thereafter), and monthly consultations with a primary care physician. Control group participants attended monthly consultations with a primary care physician who received a brief training on obesity. Forty-three (57%) participants completed the 12 months of study. After 12 months, mean changes (95% confidence interval) in body weight for the lifestyle group and the control group were -0.8 kg (-3.2, 1.5) vs +5.6 kg (3, 8.2; P<0.001) and mean changes in BMI were -1.8 (-2.6, -0.9) vs +0.4 (-0.5, 1.3; P<0.001), respectively. Intention-to-treat analysis at 12 months confirmed significant differences in primary outcomes (weight -3.5 kg, P=0.02; BMI -1.2, P=0.03) in favor of the lifestyle group. This study provides preliminary evidence that primary care physicians supported by a registered dietitian and a behavioral curriculum can be a successful strategy for treating pediatric obesity in the primary care setting.

Could giardiasis be a risk factor for low zinc status in schoolchildren from northwestern Mexico? A cross-sectional study with longitudinal follow-up.

BackgroundBoth giardiasis and zinc deficiency are serious health problems worldwide. In Mexico, the prevalence of G. intestinalis was estimated at 32% in 1994. It remains a health problem in northwestern Mexico. Recent surveys (1987, 1995, and 1999) reported zinc deficiency in the Mexican population. The association of giardiasis and malabsorption of micronutrients has been well documented, although the association with zinc remains controversial. This study investigated the association between giardiasis and zinc deficiency in schoolchildren from northwestern Mexico.MethodsWe combined a cross-sectional design with a longitudinal follow-up six months after parasite treatment. The baseline sample consisted of 114 schoolchildren (mean age 8.8 yr) from seven suburban public schools, grouped as Giardia-free (n = 65, 57%) and Giardia-infected (n = 49, 43%). Three stool analyses per child were done using Fausts method. Children with giardiasis received secnidazole. Serum zinc was determined by atomic absorption spectrophotometry. Height and weight were measured. Socioeconomic information was obtained in an oral questionnaire, and daily zinc intake was assessed using 24 hour-recalls. Pearsons correlation and ANCOVA and paired t-test analyses were used to determine the association between giardiasis and zinc status.ResultsLongitudinal analysis demonstrated a significant increase of the mean serum zinc levels in the Giardia-infected group six months after treatment (13.78 vs. 19.24 μmol/L μmol/L; p = 0.001), although no difference was found between the Giardia-free and the Giardia-infected groups (p = 0.86) in the baseline analysis. Z scores for W/A and H/A were lower in the Giardia-infected than in the Giardia-free group (p < 0.05). No difference was observed in the socioeconomic characteristics and mean daily intakes of zinc between the groups (p > 0.05).ConclusionsGiardiasis may be a risk factor for zinc deficiency in schoolchildren from northwestern Mexico.

Differences in insulin resistance in Mexican and U.S. Pima Indians with normal glucose tolerance.

CONTEXT Insulin resistance is a major risk factor for the development of type 2 diabetes in Pima Indians, a population with the highest prevalence of type 2 diabetes mellitus in the world. Their Mexican counterpart, living a traditional lifestyle in the mountains of Sonora, have at least 5 times less diabetes than the U.S. Pima Indians. OBJECTIVE We evaluated whether Mexican Pima Indians had lower insulin resistance than U.S. Pima Indians. DESIGN AND PATIENTS We compared fasting insulin and homeostasis model assessment for insulin resistance (HOMA-IR) in 194 Mexican Pima Indians (100 females, 94 males) and 449 U.S. Pima Indians (246 females, 203 males) with normal glucose tolerance from a cross-sectional study. Adjusted differences of log-transformed outcomes (fasting insulin and HOMA-IR) between groups were evaluated using multiple linear regression models and paired t test in a matched subset. RESULTS Unadjusted fasting insulin and HOMA-IR were much lower in the Mexican Pima Indians than in their U.S. counterparts. After adjusting by obesity, age, and sex, mean (95% confidence interval) for fasting insulin was 6.22 (5.34-7.24) vs. 13.56 μU/ml (12.27-14.97) and for HOMA-IR 1.40 (1.20-1.64) vs. 3.07 (2.77-3.40), respectively, for Mexican Pima and U.S. Pima Indians. Results were confirmed in subset matched for age, sex, and body fat. CONCLUSION Our results indicate that Mexican Pima Indians have lower insulin resistance in comparison with their genetically related U.S. counterparts, even after controlling for differences in obesity, age, and sex. This finding underscores the importance of lifestyle factors as protecting factors against insulin resistance in individuals with a high propensity to develop diabetes.

Impacto de un programa de desayunos escolares en la prevalencia de obesidad y factores de riesgo cardiovascular en niños sonorenses

Objective. To determine the effect of a School Breakfast Program on obesity and some cardiovascular risk factors in 6 to 10 year old schoolchildren. Material and Methods. A quasi-experimental prospective study was conducted in 2002-2003, in 17 municipalities of Sonora State, Mexico. The intervention group consisted of 254 children participating in a School Breakfast Program (SBP group). The control group (NSBP group, n=106) included children who did not participate in the program. In both groups the body mass index for age (BMI/age) and body composition by electrical resistance using bioelectrical bioimpedance analysis (BIA) were estimated at the beginning and at the end of a 9-month period. In a subgroup of 264 school-children (SBP and NSBP children), serum cholesterol, triglycerides and fasting glucose were measured at the start and at the end of the program. Results. The body mass index in the SBP and NSBP groups was not different at the start or at the end of the school period (p>0.05). The proportion of overweight and obese children and the percentage fat remained similar in both groups. However, the lean mass increased (p>0.05) at the end of the school period in both groups, and hence, cannot be attributed to the program. The biochemical parameters showed no change (p>0.05) in blood glucose, total serum cholesterol, and triglycerides in either group at the end of the school period. Conclusions. Study results

Body composition by hydrometry (deuterium oxide dilution) and bioelectrical impedance in subjects aged >60 y from rural regions of Cuba, Chile and Mexico

BACKGROUND: In Latin American and Caribbean countries such as Chile, Mexico and Cuba, the population over 60 y has increased steadily. In this age group, there is scarce information about body composition, particularly for those living in rural areas.OBJECTIVE: The purpose of this study was to determine body composition in free-living and healthy elderly subjects >60 y from rural areas of Chile, Cuba and Mexico using deuterium oxide dilution and bioelectrical impedance (BIA) and to develop and cross-validate a predictive equation for this group of subjects by BIA for future use as a field technique.SUBJECTS: The study included 133 healthy subjects (73 males and 60 females) >60 y from rural regions of Cuba, Chile and Mexico.MEASUREMENTS: Total body water, body weight, height and other anthropometric and BIA variables (resistance and reactance) were measured.METHODS: Total body water was determined by deuterium oxide dilution, and fat-free mass (FFM)/fat mass were derived from this measurement. The total sample was used in a split-sample internal cross-validation. BIA and other anthropometric variables were integrated to multiple regression model to design the best predictive equation, which was validated in the other sample. ANOVA, multiple regression and Bland and Altmans procedure were used to analyze the data.RESULTS: Body weight, percentage of fat and fat-free mass were lower in the Cuban men and women compared with Chilean and Mexican men and women. The best predictive equation of the FFM was: FFM kg=(−7.71+(H 2/R × 0.49)+(country or ethnicity × 1.12)+(body weight × 0.27)+(sex × 3.49)+(Xc × 0.13)), where H 2 is height2 (cm); R is resistance (Ω); country: Chile=1, Mexico=2 and Cuba=3; sex: women=0 and men=1; body weight (kg) and Xc is reactance (Ω). R 2 was 0.944 and the root mean square error (RMSE) was 2.08 kg. The mean±s.d. of FFM prediction was 44.2±9.2 vs 44.6±10.1. The results of cross-validation showed no significant difference with the line of identity, showing that the predicted equation was accurate. The intercept (=–0.32) was not significantly different from zero (P=0.89) and the slope (=1.02) not significantly different from 1.0 (P>0.9). The R 2 was 0.86, RMSE=3.86 kg of FFM and the pure error was 3.83.CONCLUSION: The new BIA equation is accurate, precise and showed good agreement. The use of this equation could improve the estimates of body composition for the elderly population for these regions, as well as enhancing the opportunity to conduct studies in the elderly population from Latin America.

Four-compartment model and validation of deuterium dilution technique to estimate fat-free mass in Mexican youth

OBJECTIVE To validate the measurement of fat-free mass (FFM) with the deuterium oxide (D(2)O) dilution technique (2C) against the four-compartment (4C) model in Mexican children. METHODS This was designed as a cross-sectional, non-probabilistic study. Sixty subjects (30 male and 30 female) 6-14 y of age were recruited and completed the study during 5 mo. Total body water was measured using the D(2)O dilution technique and FFM was calculated using Fomons (6-10 y) and Lohmans (11-14 y) hydration constants. Body composition using the 4C model was calculated with Lohmans equation. RESULTS Group mean accuracy showed no differences in FFM determined by D(2)O dilution and the 4C model (1.24 kg, P > 0.4), by gender (2.1 kg, P > 0.2), or by method-by-gender interaction (P > 0.7). FFMs were 26.9 and 25.7 kg by the 4C and 2C models, respectively. The test for coincidence of slopes and intercepts between the 2C and 4C models and the line of identity were not different (P > 0.05). Precision by R(2) explained 98% of the variance (standard error of the estimate 1.2 kg). Bias for the difference in FFM was not significant (-1.27, 95% confidence interval -1.5 to -0.9) and no association between the mean of the differences and the magnitude of the measurements was found (P > 0.05). Mean bias was -1.27 kg for FFM (P > 0.05), and limits of agreement were -3.1 to 0.8 kg. CONCLUSION The D(2)O dilution technique used with these hydration constants was accurate, precise, and free of bias in Mexican children and adolescents compared with the 4C model.

Environmentally Driven Increases in Type 2 Diabetes and Obesity in Pima Indians and Non-Pimas in Mexico Over a 15-Year Period: The Maycoba Project

OBJECTIVE The global epidemics of type 2 diabetes and obesity have been attributed to the interaction between lifestyle changes and genetic predisposition to these diseases. We compared the prevalences of type 2 diabetes and obesity in Mexican Pima Indians, presumed to have a high genetic predisposition to these diseases, to those in their non-Pima neighbors, both of whom over a 15-year period experienced a transition from a traditional to a more modern lifestyle. RESEARCH DESIGN AND METHODS Prevalence of diabetes, impaired fasting glucose, impaired glucose tolerance, and obesity in Mexican Pimas (n = 359) and non-Pima Mexicans (n = 251) were determined in 2010 using methods identical to those used in 1995. RESULTS During this 15-year period, age-adjusted diabetes prevalence was unchanged in Pima men (5.8% in 1995 vs. 6.1% in 2010) yet increased in non-Pima men from 0.0 to 8.6% (P < 0.05). Diabetes prevalence tended to increase in both Pima women (9.4 vs. 13.4%) and non-Pima women (4.8 vs. 9.5%). Age-adjusted prevalence of obesity increased significantly in all groups (6.6 vs. 15.7% in Pima men; 8.5 vs. 20.5% in non-Pima men; 18.9. vs 36.3% in Pima women; 29.5 vs. 42.9% in non-Pima women). CONCLUSIONS Type 2 diabetes prevalence increased between 1995 and 2010 in non-Pima men, and to a lesser degree in women of both groups, but it did not increase in Pima men. Prevalence of obesity increased among Pimas and non-Pimas of both sexes. These changes occurred concomitantly with an environmental transition from a traditional to a more modernized lifestyle.