(1) objectives: The aim of this clinical trial study is to evaluate the effects of glycemic and lipid parameters of the two protocols on WL in obese and overweight people. (2) Design: In the beginning, individuals have been selected from a nutrition clinic (Ahvaz, Iran). The initial screening had been done after a brief explanation of the study, and preliminary evaluation had been done by phone. After that a meeting with complete description of the protocol and justification for the study has been done for volunteers. The final screening was carried out in accordance with inclusion and exclusion criteria. (3) Setting and conduct: Eligible individuals after filing the consent form have been divided randomly into two groups: rapid and slow weight loss (WL). Prior to WL, an ambulatory period was imposed for each subject to insure stabilization of body weight (±2 kg during 4 weeks). During the body weight stabilization, a 3-day food dietary records was used to determine an individual’s daily food and beverage consumption to estimate their total daily caloric intake. The subjects have been randomly divided into two groups (Rapid WL and Slow WL). (4) Participants including major eligibility: Inclusion criteria were: lack of physical activity, no smoking, no alcohol drinking, no usage of herbal supplements and vitamins, and lack of weight changes in the last 6 months. Exclusion criteria included pregnancy and breastfeeding, use of drugs for metabolism, lipid and glycemic profile affects, diabetes, cardiovascular disease, kidney problems, thyroid, digestive, and respiratory diseases and cancer. (5) Interventions: Rapid WL and slow WL based on the lost weight (at least 5 %) have been defined over a period of 5 weeks and 15 weeks, respectively. The prescribed low calorie diet contained 15% as protein, 30 to 35% as fat and 50 to 55% as carbohydrate. (6) Main outcome measures: At the end of the study, anthropometric and biochemical assessments haven been conducted on individuals who reached desired WL.