When you're stressed, your body produces stress hormones and this can block weight loss. This is sometimes referred to as the famine effect. When you're stressed, your body interprets prolonged stress as famine even though you're taking in adequate nutrients. The body then goes into hoarding mode. Stress can be physical, emotional or even diet-related. When you binge, restrict your calorie intake severely or yo-yo diet, these are also other forms of stress that can block weight loss. Diet pills like Decaslim are popular because some people want instant results. These are usually not the best way to lose weight because of unknown side effects and what not. So at the risk of being repetitive, the best way to lose weight is to practice portion control and lead an active lifestyle.