BACKGROUND: In 2014, Mexico implemented an 8% tax on non-essential energy-dense foods (NEDFs) exceeding 275 calories per 100 g to improve dietary quality and reduce obesity prevalence. While this tax has shown promising results in reducing purchases of these items and decreasing obesity rates in children, its potential may be limited by the relatively low tax rate. We aimed to assess the potential impact of increasing the existing NEDF tax on body weight (kg), body mass index (BMI), obesity prevalence, and obesity cases in the Mexican adult population. METHODS: Using data from the Mexican 2018 National Health and Nutrition Survey (ENSANUT-2018), and a microsimulation mathematical model that translates adult energy balance into body weight changes, we analyzed the potential impact on obesity over 10 years. Our final sample included 15,109 participants, representing approximately 76,221,919 adults aged 20 and older in Mexico. RESULTS: We found that doubling the existing tax (16%) could result in an average weight reduction of 0.4 kg and a 3.2% reduction in obesity prevalence over 10 years. If the NEDF tax was quadrupled (32%), an average weight loss of 1.2 kg and an 8.8% reduction in obesity prevalence could be expected. Males, low-income individuals, and adults aged 20 to 39 years would benefit the most, showing a higher expected reduction in obesity. CONCLUSIONS: Very few examples of taxation on NEDFs exist worldwide, and Mexico has been a key example. Policymakers should consider a tax reform that increases the current NEDFs tax to achieve larger health benefits.