Paleo eating doesn't guarantee weight loss, nor does it even prevent weight gain. It's a food philosophy that affects your food choices. Without an added element of calorie-reduction, you may lose little or no weight.
If you eat a lot of processed foods, switching to paleo might result in weight loss without any other behavior changes. However, if you already eat mostly whole foods, converting to paleo may not help with weight loss unless you add calorie reducing strategies.