Customer satisfaction in the fast food industry of the United Kingdom leads to brand loyalty, which positively impacts profitability. Satisfied customers are less price sensitive, more likely to buy additional products, and less likely to switch to competitors. Retaining just 5% more customers can increase profits by 25-125%. To study this relationship, data was collected from customers of five popular fast-food restaurants through surveys. The findings show that happy customers are key to a successful business in the fast food industry.