(Bueno, et al., 2013) An experiment was carried out to determine the effective way for overall weight loss. A total of 609 participants who were involved in this experiment were all older than 18 years old. Participants in this experiment didn’t have any major diseases such as diabetes, cancer, and high cholesterol. The participants followed a restricted diet with less than 30 % of energy from fat and a diet with no more than 50g of carbohydrates. Participants were instructed to minimize the intake of sugar, refined flours and trans-fat and concentrate on foods that are minimally processed and full of nutrient. The experiment lasted for 12 months and the participants had a mean BMI greater than 27.5 kg/m2. In this experiment, the subjects were not limited to their race or sex.
The analysis aimed to calculate the differences in the outcomes of the prescribed diets. The main data that was sought in this experiment was the mean change between the baseline body weight and the final body weight (in kg). The changes which was the difference in values between the final and baseline mean were analyzed. The effects of this experiment were gathered and weighted mean differences (WMD) were calculated. The calculations were performed using a random effects model (DerSimonian, R ; Laird, N, 1986). A value of 0.05 is considered to be an above average value.
Heterogeneity among the studies was tested using the Cochran Q test, and inconsistency was tested using the I 2 test. A value less than 0.10 is considered to be significant. Whenever a result showed heterogeneity, it was further analysed in two different ways. One of the methods was to remove each study one at a time to determine if the removed study explained the heterogeneity. Afterwards, studies who shared similar methodological features, were further grouped into subgroups and analysed further. These subgroup analyses were performed despite the presence of any heterogeneity.

A flow chart diagram based on the process of randomized controlled trials (as cited by BMJ, 2010).