Comparison of plasma malondialdehyde and glutathione levels between low calorie high protein diet to standard protein in obese individuals with weight cycling – a randomised trial [version 1; peer review: Peer review discontinued]

Background: Increasing BMI increases the risk of developing cardiovascular and metabolic diseases. Oxidative stress is believed to be the underlying mechanism. A significant proportion of people who have previously succeeded in reducing body weight acquire subsequent weight gain (weight cycling). The current study aimed to evaluate the effects of low calorie diets, either with high or standard protein on plasma malondialdehyde (MDA) and glutathione (GSH) levels in obese people with a history of weight cycling. Methods: A clinical trial was conducted in a worker’s health centre in Jakarta. Participants were assigned to a caloric restriction diet, with two different intervention groups; a high protein/HP group (22-30% of total caloric intake from protein) and a standard protein/SP group (12-20% protein). The diet programme was applied for 8 weeks with daily reminders and weekly counselling. 61 participants were recruited. 54 participants completed the programme but only 15 subjects had their MDA and GSH level measured pre- and post-treatment. Plasma MDA and GSH levels were measured according to Will’s method and Ellman’s method, respectively. Results: The mean changes of MDA levels after completing the diet programme in the HP and SP group were 0.031 + 0.124 and -0.034 + 0.363 nmol/ml plasma, respectively. Meanwhile, the mean changes of GSH levels in the HP and SP group were -0.059 + 0.1673 and -0.034 + 0.363 µg/ml plasma, respectively. No statistical significance were found between the mean difference of plasma MDA and GSH level changes among both groups. Conclusions: Changes in MDA and GSH levels after high protein or standard protein low-calorie diet intervention for 8 weeks were not significantly different. Protein proportion in the low calorie diet does not affect the change in oxidative stress state for obese individuals with weight cycling.