The prevalence of obesity is increasing in many countries and has become a public health challenge in populations worldwide. It is estimated that at least one billion of individuals worldwide are overweight (body mass index, BMI ≥ 25 kg/m²) and at least 300 million are obese (BMI ≥ 30 kg/m²) 1 2 . The prevalence of obesity has specially increased in populations in developing countries; for example, a recent survey carried out in Mexico found that the prevalence of obesity in adults in 2006 was 24.2% in men and 34.5% in women, increasing 4% in only 6 years 3 4 .

Recent studies have suggested that micronutrient deficiencies might be associated with a higher susceptibility for obesity which might partially explain why obesity in poor countries has increased more rapidly 5 . The possible association of some micronutrient deficiencies with a higher susceptibility for fat deposition and obesity has recently been revised 6 . Since calorie restricted diets might worsen micronutrient deficiencies, a strategy to reduce calories in obese population with a high probability of having some micronutrient deficiencies, should contemplate increasing the intake of vitamins and minerals.

Low calorie diets (LCD) and an increase in physical activity are effective strategies to reduce body fat and to control body weight 7 ; however a high proportion of individuals trying to lose weight find it very difficult to reduce energy intake 8 . Partial meal replacements (PMR) are single food or selection of foods intended as replacement of one or two daily meals to reduce energy intake. PMR are made with variety of food preparations, they can be liquid or powder formulas, frozen foods or bars fortified, all fortified with vitamins and minerals 9 . In addition to energy intake reduction, PMR have been used to increase the intake of vitamins, minerals and proteins and thus decrease the risk of deficiencies that are common during energy restriction diets 10 11 . Several studies have evaluated the effectiveness of PMR to reduce weight among obese individuals with different results 10 12 . Most of these studies however, have been carried out in developed populations with a low risk of having micronutrients deficiencies.

Besides the addition of vitamins and minerals, the effectiveness of PMR may be improved by being used as a vehicle for substances with a potential benefit for the obese. Inulin is a non-digestible and non-flavored polisaccharide with low energy content that has been shown to have a positive effect on lipids metabolism 13 14 15 16 17 18 19 20 . A recent meta-analysis by Brighenti 21 reviewed 15 studies and concluded that supplementing individuals with 7 to 10 g/d of inulin reduces their serum triglycerides by 7.5%. A reduction of triglycerides in obese patients would be beneficial since about 36% of individuals with obesity have high serum triglycerides 22 . It has also been suggested that inulin may increase the absorption of minerals such as zinc, iron, magnesium and calcium 23 .

The objective of this study was to test the efficacy of a PMR added with vitamins, minerals and inulin on weight reduction, blood lipids and micronutrients intake in obese Mexican women.

Flow diagram of participants is shown in Figure 1. The subjects that did not finish the intervention, abandoned the study for personal reasons not related to the treatment. Characteristics of subjects by treatment group at the beginning of the study are described in Table 2. No differences were observed between groups in any of the study variables at baseline or between subjects that were lost to follow up and subjects that remained to the end of the study.

¹ Values are means ± Standard deviation.

² There were no significant differences between treatment groups in ANOVA.

PMR = Partial meal replacement, INU = Inulin, CON = Control group.

Results of PMR effect on body weight have been controversial. Recent revisions and meta-analysis suggest that their use have a moderate effect resulting in weight loss of around 9%–10% of total body weight in the short term (3–6 months), and 6%–8% in the long term (> 1 years), when used as part of an overall low-energy diet plan 11 12 17 34 . Our results showed that the inclusion of PMR alone or in combination with inulin to a LCD was equally effective to reduce weight compared to LCD alone. After 90 days, both groups with PMR lost an average of 4 Kg or about 5.4% of initial weight. This reduction was about 28% higher than the reduction with the LCD alone but the difference was not statistically significant. Similarly to our results Noakes 35 compared a group of obese men with PMR and LCD with a group with LCD alone and found after 3 months, a loss of body weight of 6.6 Kg (6.9%) and 6.0 Kg (6.3%), respectively. Another study in obese women found after one year of treatment a weight reduction of 5.0 Kg (6.2%) with PMR plus LCD and 6.1 Kg (8%) with LCD alone; the difference was not statistically significant 10 . Two previous studies 11 found reductions in average weight of 7.1 kilograms after 3 months or 7.7 kilograms after one year with the inclusion of PMR to a LCD ; but in these studies the effect was significantly higher than LCD mainly because the effect of LCD was very low (1.3 and 3.4 kilograms, respectively). One recent study found a significant positive effect on weight reduction by the inclusion of PMR to a LCD 36 . Obese subjects lost in average 13.5 kilograms (12.3%) with LCD plus PMR compared with 6.5 kilograms (6.7%) with LCD alone after 16 weeks. In this study, subjects had an average BMI at the beginning of the study of 38 Kg/cm², which was much higher than the baseline average BMI in our study of 31 Kg/cm². This suggests that the inclusion of PMR to an LCD is more effective when subjects are “more obese”.

Treatments with PMR, PMR + I and INU significantly reduced triglycerides after 3 months of treatment. Both groups with inulin and PMR alone had an effect, so this could be attributed to inulin or its combination with a loss of body fat. Of 11 studies reviewed by Delzenne 13 on the effect of inulin on blood lipids, 4 studies did not find an effect of inulin on total cholesterol and triglycerides, 3 studies showed significant reduction in triglycerides, and 5 studies showed a modest reduction in total cholesterol and LDL cholesterol. Brighenti 21 conducted a meta-analysis that included studies and concluded that the intake of inulin was associated with significant decreases in serum triglycerides of 0.17 mmol/L (15 mg/dL) or 7.5%. Brighenti 16 found a marked reduction on plasma triglycerides and moderate decrease in plasma cholesterol in twelve healthy men consuming 9 g inulin/d. Letexier et al. 18 observed a 16% decrease in plasma triglycerides in eight subjects consuming 10 g inulin/d. In the present study, a significant reduction of 21.3%, 21.9% and 20.3% of plasma triglycerides was found with PMR + I, PMR and INU groups. In average, our subjects did not show elevated concentration of cholesterol or triglycerides at the beginning of the study; thus the effect that we found in reducing triglycerides could be more important in obese subjects that have high lipids concentrations as has been reported in other studies 19 20 37 38 .

Total energy and carbohydrates intakes decreased similarly in all groups and fat intake, including cholesterol, was reduced significantly more in both groups with PMR compared with INU and CON groups. Ditschuneit 11 found similar results; PMR reduced cholesterol intake 17% more than a group with LCD alone and fat intake decreased significantly 48% in the PMR group and the control group decreased 19%. Also, Ashley 10 found a decrease in the intake of saturated fat and cholesterol by the inclusion of PMR. As expected, PMR + I and INU groups significantly increased total fiber intake from 13.9 to 17.5, and 13.6 to 20.8 g/d per day, respectively. An increase in dietary fiber intake is highly recommended in obese subjects 39 . These results suggest that PMR added with inulin can contribute with a reduction in fat intake and an increase in dietary fiber intake which could be beneficial in obese individuals with a higher risk of developing hyperlipidemia, or insulin resistance.

An important finding of this study is that PMR could contribute to increase the intake of essential nutrients, which is especially important during caloric restriction and in populations that need to reduce calories but that are at risk of having micronutrient deficiencies. In Mexico for example, there is a high prevalence of obesity, about 30% of adults and 16% of children less than 12 years are obese 4 ; and in many individuals, obesity occurs simultaneously with some micronutrient deficiencies 6 ; prevalence of some micronutrient deficiencies documented in Mexican adults are: 27% in zinc, 34% in vitamin E, 34% in vitamin C, 20% in vitamin B2 and 20% have iron deficiency 40 41 42 . Treatments with PMR increased intake of vitamins and minerals compared with LCD alone, especially calcium, iron, magnesium, zinc, vitamin B1, B2, B6, B12, niacin, folic acid and vitamin C and contribute to meet recommendations of such nutrients during LCD´s . Because PMR is prepared with skimmed milk, the groups that included PMR increased milk and calcium intake. Calcium intake increased 20 and 30% in the PMR + I and PMR groups, respectively. Long term use of LCD´s have been associated with bone resorption in obese adults due to low intake of calcium which can lead to bone demineralization 43 . Treatments with PMR increased intake of vitamins and minerals compared with LCD alone, especially calcium, iron, magnesium, zinc, vitamin B1, B2, B6, B12, niacin, folic acid and vitamin C and contribute to meet recommendations of such nutrients during LCD´s . Because PMR is prepared with skimmed milk, the groups that included PMR increased milk and calcium intake. Calcium intake increased 20 and 30% in the PMR + I and PMR groups, respectively. Long term use of LCD´s have been associated with bone resorption in obese adults due to low intake of calcium which can lead to bone demineralization 43 . This is one of the reasons why intake of calcium supplements and/or milk has been found to have beneficial effects on mineralization during prolonged LCD´s 44 45 . Our study suggests that the use of PMR´s could contribute to meet recommended intakes of nutrients specially when there is need to reduce calorie intake and in individuals with micronutrient deficiencies.

As it is common in dietary intake data, there was a considerable variability in the nutrient intake data, even when some statistical differences were found, some micronutrient comparisons were low powdered because the sample size was calculated upon body weight. In addition, the study did not find body fat change statistically different between treatments, it has been documented that other methods such as DEXA could have provided more accurate results 46 . Since this study was not intended to confirm the improvement of nutrient status, more studies are needed to evaluate if increased nutrient intake also increases micronutrient absorption and improves micronutrient status.

In conclusion, we found no additional effect of including PMR or a PMR added with inulin to a calorie restricted diet on changes in body weight, BMI or fat loss, than a LCD alone; however, intake of PMR, PMR added with inulin or inulin alone contribute to reduce plasma triglycerides during calorie restriction. In addition, treatment of obesity with LCD that includes a PMR significantly increased intake of essential amino acids, vitamins and minerals and contributed to meet daily recommendations. Results of the present study are particular relevant for populations that have increased prevalence of obesity and that at the same time have high prevalence of micronutrient deficiencies. This study points out the importance of using adequately fortified meal replacement products to ensure nutrient adequacy during energy intake restriction for weight loss.

PMR: Partial meal replacement; PMR + I: Partial meal replacement with inulin; INU: Inulin; CON: Control group; LCD: Low calorie diet; ANOVA: Analysis of Variance.

This study was partially financed by Nucitec SA de CV. MAD was an employee at this company and did not receive any compensation for this study. JLR owns shares of this company. Both participated in the concept and design of the study and providing intellectual interpretation of the results.

ART conducted the fieldwork and wrote the initial draft of the paper; MCC contributed with the data analysis and its interpretation as well as with the writing of the manuscript; SG participated in the design of the study and quality assurance; MAD participated in the concept and design of the project; JLR participated in the concept and design and revised critically and intellectually the manuscript. All authors read and approved the final manuscript.