Is sattu helpful in weight reduction?

Not sure. It is not a supplement, it is a food from south asia and mixed with pulses and cereals. Sounds healthy and eating healthy is a start to losing weight.
Calories in - out. Weight loss is all about calories out > calories in, plain and simple. Consumer reports had a great summary article here http://www.Consumerreports.Org/health/healthy-living/diet-nutrition/diets-dieting/diet-tips/overview/index.Htm. Whatever helps you reduce your calorie intake (safely) is a good intervention.