Obesity, physical inactivity and poor nutrition are important risk factors for non-communicable diseases such as type 2 diabetes, cardiovascular disease and some cancers. Social marketing campaigns can raise awareness of these risk factors and promote behaviour change but must compete for share of voice in an increasingly complex and cluttered media environment. Commercial advertising for products and services may dilute or even undermine public health messages by presenting a distorted view of foods and activities available and their associated health benefits. We know food and beverage advertising in Australia is dominated by unhealthy products, with sugary drinks among the most heavily advertised. Data is needed on other food and diet-related product advertising. Artificially sweetened drinks offer a lower-kilojoule alternative, but their overall benefit to weight loss and chronic disease prevention is dubious. Likewise, some commercial products and services with purported weight loss benefits (including ‘diet’ meals and snacks, meal replacements, weight loss or fitness programs and products with purposed ‘fat burning’ or ‘appetite suppressant’ qualities) may be effective for weight loss or behaviour change, however others may be ineffective or even detrimental to health. Using estimates from a media monitoring company, this study aims to compare advertising expenditure for (a) obesity prevention, physical activity, and/or healthy diet public health campaigns with commercial advertising for (b) sugary drinks, (c) artificially-sweetened drinks, and (d) diet/weight loss products and services in Australian media from 2016 to 2018. Expenditure will be compared between advertising categories and within different media channels (television, outdoor, cinema, radio, newspapers, magazines and limited online) to describe the Australian advertising landscape in relation to obesity prevention and promotion of healthy diet and physical activity.