There has been a growing concern about obesity worldwide. We performed a review on the prevalence and trends of obesity among adults and children. We reviewed the data on the prevalence of adult obesity and being overweight from the Global Database on Body Mass Index on the World Health Organisation (WHO) Website and prevalence of children being overweight from the International Obesity Task Force website. Various databases were also searched for relevant reviews and these include PubMed, EMBASE, NHS CRD databases and Cochrane. The prevalence of obesity is high in many parts of the world. Generally, there is an increasing trend of prevalence of adult obesity with age. The peak prevalence is reached at around 50 to 60 years old in most developed countries and earlier at around 40 to 50 years old in many developing countries. Obesity is a major health concern. Appropriate strategies need to be adopted to tackle obesity which itself brings about significant disability and premature deaths. Further observation may be needed to see if the trend of prevalence abates or increases in the near future.