Effect of Specific Diet and Physical Activity on Weight and/or Fat Loss

The main purpose of this study is to assess metabolic effects (decreased amount of body fat content, insulin sensitivity and lipid profile improvement) of weight loss intervention based on specific life style counseling (low calorie "metabolic stairs" diet and circuit-based exercise in a comparison to conventional diet and exercise. The main hypothesis is that more significant beneficial metabolic effects will have specific life style counseling effect than conventional diet and exercise. The main purpose of this study is to assess above mentioned metabolic changes before and after 6-8 weeks of weight loss intervention. The investigators will also study the following: 1. The impact of life style counseling induced weight and/or fat loss on physical fitness 2. The impact of life style counseling induced weight and/or fat loss on metabolic parameters (e.g. insulin sensitivity, lipid profile, ect.)