A low-glycemic diet is crucial for those with diabetes and cardiovascular diseases. Information on the glycemic index (GI) of different ingredients can help in designing novel food products for such target groups. This is because of the intricate dependency of material source, composition, food structure, and processing conditions, among other factors, on the glycemic responses. Different approaches have been used to predict the GI of foods, certain discrepancies exist because of factors including the inter-individual variation among human subjects. Besides other aspects, it is important to understand the mechanism of food digestion because an approach to predict GI must essentially mimic the complex processes in the human gastrointestinal tract. The focus of this work is to review the advances in various approaches for predicting the glycemic responses of foods. This has been explained by detailing conventional approaches, their merits and limitations, and the need to focus on emerging approaches. Given the fact that no single approach can be generalized for all applications, the review emphasizes the scope of deriving insights for improvements in methodologies. Reviewing the conventional and emerging approaches for the determination of GI in foods, this detailed work is intended to serve as a state-of-the-art resource for food and nutritionists who work on developing low GI foods.