Effect of a low glycemic load on body composition and Homeostasis Model Assessment (HOMA) in overweight and obese subjects

Efecto de la baja carga clucémica en la composición corporal y el HOMA en sujetos con sobrepeso y obesidad

A. L. Armendáriz-Anguiano^1,2, A. Jiménez-Cruz^1,2, M. Bacardí-Gascón^1,2 and L. Hurtado-Ayala³

¹Faculty Members of Medicine and Psychology School.
²Member of Nutrition Academic Group.
³Faculty Member of Chemical Science and Engineer School. Universidad Auntónoma de Baja California. Tijuana B. C. México.

ABSTRACT

Objective: The aim of this study was to compare the effects of different glycemic load diets on biochemical data and body composition, in overweight and obese subjects, during a 6-month period.
Research design and methods: This study was an experimental, randomized, parallel design. Anthropo-metric measurements and biochemical data were measured at baseline at 3 and at 6 months. All subjects completed 3-day dietary intake diaries at the baseline period and during the third and the sixth months. At the sixth month, LGL group had a mean intake of 1,360 ± 300 kcal/day and the high glycemic load group (HGL) had a mean intake of 1,544 ± 595 kcal/day.
Results: LGL group obtained a weight reduction of 4.5% (p = 0.006) and the HGL group of 3.0% (p = 0.18). Significant reductions in waist circumference (5%, p = 0.001) of the LGL group were observed, 10% of body fat percentage (p = 0.001), 4.3 kg (13%) of body fat (p = 0.001), 14% of total cholesterol (p=0.007), 35% of high-density lipoproteins (HDL) (p = 0.001), and 10% of HOMA (p = 0.009). In the HGL group, reductions of 4.5% of waist circumference (p = 0.02), 37% of HDL (p = 0.002), and an increase of 8 % of LDL (p = 0.04) were observed.
Conclusions: These results suggest that long term LGL diets are more effective for reducing body mass index, body fat, waist circumference and HOMA and, therefore, may contribute in the prevention of diabetes.

Key words: Glycemic load. Obesity. Overweight. Diabetes.

RESUMEN

Palabras clave: Carga glucémica. Obesidad. Sobrepeso. Diabetes.

Abréviations

Gl: Glycemic Index.
LGI: Low glycemic index.
LGL: Low glycemic load. ]]> HGL: High glycemic load.
GL: Glycemic load.
CHD: Coronary heart disease.
TC: Total cholesterol.
HDL: High-density lipoproteins.
TG: Triglycerides.
BMI: Body mass index.
HOMA: homeostasis model assessment.
LDL: Low-density lipoproteins.
INUBAC: Instituto de Nutriciön de Baja California. ]]> WC: Waist circumference.
IPAQ: International Physical Activity Questionnarie.
RCT: Randomized controlled trials.

Introduction

Insulin resistance is one of the main effects on human health, resulting from weight gain, and plays a principal role in the development of the metabolic syndrome.¹ It is also an important risk factor in the development of type 2 diabetes mellitus and cardiovascular diseases.² Additionally, in a study by Oster et al.,³ it was estimated that 85% of all cases of type 2 diabetes were attributable to overweight and obesity. Regular consumption of high glycemic index (GI) foods can also increase the risk for obesity, type 2 diabetes, cardiovascular diseases and some types of cancer.⁴ Some studies have demonstrated the beneficial effect of low glycemic index (LGI) and low glycemic load (LGL) diets in subjects with diabetes^5-10 and hyperlipidemias.¹¹ The glycemic load (GL) concept encompasses the idea that the overall glycemic effect of a diet may be related to disease risks.¹² Glycemic load is calculated by multiplying the GI by the amount of carbohydrates consumed.¹³ Van Dam et al.¹⁴ carried out a study in elderly healthy men and did not observe an association between high GI diets and the incidence of coronary heart disease (CHD), total cholesterol (TC), high-density lipoproteins (HDL), triglycerides (TG), insulin or glucose. On the other hand, Ebbeling et al.¹⁵ observed a decrease in body mass index (BMI), fat mass and a lesser increase in insulin resistance with LGL diets during a 3-month interventional period and 6 months follow-up. Furthermore, LGL diets have shown a decrease in fat mass and significant improvement in insulin sensitivity (HOMA) in obese subjects during a 36-week period.¹⁶

It has also been observed that, in the Mexican culture, after a 3-week intervention with appropriate diets in hyperlipidemic subjects, LGI diets decrease TC and low-density lipoproteins (LDL).¹¹ However, we have not found long-term studies analyzing the effect of LGL hypocaloric diets on body composition and insulin sensitivity. The aim of this study was to compare the effects of diets with different GL on body composition and biochemical markers in overweight and obese subjects during a 6-month period.

Research design and methods

Study procedure

Subjects

Fifty-four adults with overweight or obesity were assigned in two groups: 27 subjects with LGL diet and 27 with high glycemic load (HGL) diet. Subjects who were pregnant or had diabetes, cancer, psychiatric disorders or physical disabilities were excluded.

Diets and dietary assessment

Two diets were designed including LGL and HGL diets. GI values of each food were estimated from the tables by Foster-Powell et al.¹⁷ Daily GL was determined by the product of total dietary carbohydrate (grams) and GI of each food and adjusted to energetic intake using the following formulas: GI = (GI of each food X proportion of total carbohydrate contributed from each food); GL= (GI of each food x grams of total carbohydrate from each food)/1,000 kcal.

Diets were designed according to the food habits of Mexicans living in the Tijuana area. On the first day, subjects received different menus of either LGL or HGL diets, according to the randomization. A research assistant was available by mail or by phone for questions during the 6-month period. E-mail, as a reminder and reinforcement to maintain the diet, was sent every 2 weeks to all participants. Subjects who completed the 3-day dietary record (two weekdays and one weekend day) were included in the analysis.

Anthropometric measurements

Height was measured to the nearest millimeter using a portable stadiometer (model 214 Road Rod, Seca Corp., Hanover, MD). Weight was measured to the nearest 0.1 kg using an electronic scale (Bod Pod, Life Measurement Inc., Concord, CA). Subjects were dressed in light clothing and were without shoes. BMI was calculated with the following formula: weight (kg)/height (m²). Waist circumference (WC) was measured at the minimum circumference between the iliac crest and the rib cage. Fat mass (in kg) and total body fat percentage were measured by plethysmography with the Bod Pod. The subjects entered the Bod Pod with bodysuit and Lycra hat.

Blood analysis

Venous blood samples were taken at 8 a.m. from an antecubital vein after a 12-h overnight fast, again at baseline and at 3 months after beginning the study. Blood samples were centrifuged at 3,500 x g for 3 min, and plasma was removed and analyzed immediately after collection. For quantitative determination of glucose in serum, the glucose oxidase procedure based on a modified Trindler method was used (SERA-PAK Plus, Bayer, Sées, France). Serum insulin levels were determined by chemiluminescent immunoassay by the IMMULITE 2000 analyzer (Diagnostic Products Corporation, Los Angeles, CA). Homeostasis model assessment (HOMA) was used to estimate insulin resistance and was computed as follows: (fasting serum insulin [μU/ml] x fasting plasma glucose [mmol/L]/22.5).^18,19 Total cholesterol, HDL-cholesterol and triglycerides were measured by enzymatic methods (SERA-PAK Plus, Tarrytown, New York); LDL-cholesterol was calculated using the Friedewald formula: LDL (mmol/L) = total cholesterol -(TG/2.2) - HDL.

A questionnaire containing seven questions from the International Physical Activity Questionnaire (IPAQ)²⁰ was used to evaluate physical activity at baseline and at 1, 3 and 6 months after study initiation.

Statistical analysis

Sample size was calculated as N = 30 per group assuming 5 cm of WC at the end of the study with 80% of power and 5% of significance level. Mean ± standard deviations were calculated using descriptive statistics in all variables. Anthropometric measurements were evaluated, and it was determined that they did not meet the normality test (Kolmogorov-Smirnov and Shapiro-Wilk). To test differences between groups on biochemical and anthropometric measurements, Mann-Whitney non-parametric test for independent samples was performed. For comparison of differences before, at 3 and 6 months after intervention in the same treatment group, we used Friedman non-parametric test for repeated measurements. To test differences between groups on diet intake at baseline and at the end of the study, MannWhitney non-parametric test for independent samples was performed. All analyses were performed using SPSS software (version 11.5, Chicago, Illinois)

Results

Subject characteristics

At the beginning of the study, 54 subjects were recruited (36 females and 18 males). Baseline characteristics of the subjects are shown in table I. There were no significant differences between groups in body composition, biochemical markers and nutrient intake variables.

Fifty-four subjects were analyzed at the beginning of the study. At 3 months, 33 (61%) subjects returned for anthropometric and biochemical measurements (18 with LGL diet and 15 with HGL diet), and at 6 months 24 subjects (44%) completed the dietary intake diaries (16 with LGL diet and 8 with HGL diet) and returned for anthropometric and biochemical measurements.

Diet composition

No significant differences were observed at baseline between groups in the consumption of kilocalories, macronutrients, GI and GL. After 3 and 6 months of intervention, both groups had a significant decrease in caloric consumption (table II). Significant reductions of energy, carbohydrate, protein, GI and GL intake were observed in the LGL group after the intervention, and reduction of energy in the HGL group (table II).

Body composition and biochemical data

At 6 months LGL group obtained a weight reduction of 4.5% (P = 0.008) and the HGL group of 3.0% (P = 0.68). Significant reductions in waist circumference (5%, P = 0.001) of the LGL group were observed, 10% of body fat percentage (P = 0.002), 4.3 kg (13%) of body fat (P = 0.002), 14% of total cholesterol (P=0.007), 35% of high-density lipoproteins (HDL) (P = 0.0001), and 10% of HOMA (P = 0.009). In the HGL group, reductions of 4.5% of waist circumference (P = 0.07), 37% of HDL (0.002), and an increase of 8 % of LDL (P = 0.04) were observed (Table III).

Physical activity

There were no significant changes in physical activity at baseline or at any time point during the intervention.

Side effects

No side effects were observed with the diets.

Discussion

This study, conducted in overweight and obese men and women, showed higher beneficial effects of LGL hypocaloric diet controlled by macronutrient consumption and fiber on most body composition and biomarkers data when compared to the HGL diet. HDL was significantly reduced in both groups. A few randomized controlled trials (RCT), parallel or crossover, had been reported on the effect of GI on overweight or obese adolescents,¹⁵ young adults,^21,22 and adults,²³ which assessed the diet on a duration ranging from 9 months²³ to 29 months.²¹ The four studies compare LGI or LGL meals with low-fat meals or conventional diet. Pereira et al.,²¹ Ebbeling et al.¹⁵ included a restricted conventional diet vs. ad libitum LGL, and Maki et al.²³ included 15 intensive clinic visits and a low-fat portion-controlled diet.

In our study the energy intake was lower for both the LGI and HGI diets than the previously reported RCTs. There were no differences in the consumption of fiber and fat content of the diet as in the study conducted by Ebbeling et al.¹⁵ in obese adolescents. However, in our study, the LGL had more fiber than the adolescents in the study by Ebbeling et al.¹⁵. The groups in the study conducted by Pereira et al.²¹ had different carbohydrate, fiber, fat and protein consumption. In the study by Ebbeling et al. conducted in young adults,²² there were differences in carbohydrate and fat consumption, and in the study conducted by Maki et al.²³ there were differences in the carbohydrate and fat content of the diets.

In our study, significant differences were observed in both groups in most anthropometric measurements. The LGL group obtained a weight reduction of 4.5 % (p = 0.008) and the HGL group 3.0% (p = 0.68).

These results are consistent with those observed by Raatz et al.¹⁶ in overweight and obese subjects. In this study, after six months with LGL and LGI diets, a greater reduction in fat mass was observed with maintenance of fat-free mass and a significant improvement in HOMA, compared with HGI diets.¹⁶ The reduced effects observed on body weight, fat mass and HOMA in the LGL group are consistent with those reported by others.²² In addition, Pereira et al.²¹ and Ebbeling et al.¹⁵ also reported between-group differences on those parameters. However, the study by Pereira et al.²¹ excluded those with weight loss < 10%. In the study by Ebbeling et al.,¹⁵ a lower consumption of carbohydrate and fiber and higher consumption of fat showed a reduction in triglycerides between groups. The study by Pereira et al.²¹ also showed a reduction between groups on triglycerides, and the study by Maki et al.²³ showed a beneficial effect on HDL cholesterol. Similarly, in our study a reduction of triglycerides (18%) was shown but did not reach statistical significance (Table III); however, a decrease in HDL cholesterol was also shown in both groups without changes in physical activity. In this study, in the LGL diets showed a significant reduction in dietary GI and GL, calories, carbohydrate and protein intake, while in the HGL diets showed a significant reduction in calories. Dietary fiber consumption in both diets was maintained constant. This could imply that the changes obtained by the LGL might be attributed to the GL of the diet. These results also suggest that hypocaloric diets with LGL may be more efficient measures for the reduction of BMI, body fat, and HOMA and may contribute to the prevention of diabetes in a highly susceptible population. The limitations of this study were the low participation at the beginning of the study, low participation rate at three (61%) and six months (40%) of the intervention.

These results suggest that long term LGL diets are more effective for reducing body mass index, total body fat, waist circumference, HOMA, total cholesterol, and LDL-cholesterol; therefore, may contribute in the prevention of diabetes among subjects with Mexican dietary habits.

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Correspondence:
Ana Lilia Armendáriz- Anguiano.
Universidad Autónoma de Baja California. ]]> Calzada Universidad, 14418,
Parque Industrial Internacional.
22390 Tijuana B. C. México.
E-mail: dranita_78@hotmail.com

Recibido: 20-X-2009.
1.^a Revisión: 10-XII-2009.
Aceptado: 10-XII-2009.