With the continuous development of society, fast food has become a daily choice in modern society due to its high convenience. However, its high-calorie, high-sugar, high-fat, and low-nutrient characteristics significantly increase the risk of obesity. According to statistics, over 2.5 billion adults worldwide are overweight, and fast food consumption is recognized as an important factor driving the rise in obesity rates. This article delves into the multidimensional impact of fast food consumption on the global obesity rate and the effectiveness and challenges of controlling obesity through increasing fast food taxes. These policies face many difficulties in implementation, such as economic penalties that make it challenging to change consumption habits completely and may exacerbate the burden on low-income groups. In addition, Denmark’s saturated fat tax practice has shown that although tax policies can bring specific results, they have also caused problems such as increased unemployment and cross-border shopping. The article points out that relying solely on raising taxes is challenging to solve the problem of obesity, and multiple factors need to be considered comprehensively. The convenience, addiction, and extensive advertising coverage of fast food make it difficult for consumers, predominantly low-income and adolescent groups, to resist its temptation. Therefore, the government, businesses, and consumers need to work together to address the challenge of obesity through comprehensive measures such as strengthening health education, promoting healthy eating habits, and improving food production and processing technologies. This article also emphasizes that although tax increase measures can, to some extent, guide consumers to reduce their fast food intake, their effectiveness is limited and may lead to social and economic inequality issues. In the future, more innovative and comprehensive strategies should be explored to address the global obesity epidemic effectively.