Maguire D et al 2020 - The role of thiamine dependent enzymes in obesity and obesity related chronic disease states: A systematic review

In 2008 it was estimated that 1·46 billion adults worldwide were overweight and 502 million people were estimated to be in the obese range [1]. The WHO 2016 report indicates that these figures have significantly increased, estimating more than 1.9 billion adults are overweight (BMI>25), of which over 600 million of these are obese (BMI>30) [2]. Alarmingly, childhood obesity levels have risen in tandem with adult obesity. WHO statistics reveal that 41 million children under the age of 5 were overweight or obese in 2014 [2].

Increasing obesity is primarily due to increased consumption of calories [3], [4]. The recommended daily calorie intake is 2000 kcal and 2500 kcal for adult women and men respectively [4]. The average American consumes 3770 kcal/day and the average person in the UK consumes 3400 kcal/day [1]. These figures are steadily rising due to the ready availability of ‘high sugar, low nutrient’ foods, that characterize the North American and Western European diet [5]. Chronic calorie excess is now endemic in Western society, with a reported 35–40% North Americans having BMI's in the obese range (BMI>30) [4]. Indeed, obesity has now overtaken smoking to become the number one cause of preventable death in some of the Western nations [6], [7], [8].

The burden of obesity worldwide now poses a significant risk to population health and some experts warn that the obesity pandemic threatens to reverse the gains achieved in risk reduction for cardiovascular and cancer deaths over the past three decades [1], [4], [9]. The caloric burden on individuals in Western societies has increased as a consequence of changing diet. This has imposed a sugar rich nutritional intake on a metabolism evolved in a sugar poor evolutionary environment [10], [11], [12], [13]. Total health-care costs attributable to obesity and overweight are projected to double every decade to account for 16–18% of total US health-care expenditure by 2030 [1].

Despite the appearance of being overfed, there is now increasing evidence that this population is nutritionally depleted of essential micronutrients and vitamins [14], [15], [16]. In 2012 the National Research Council reported that >80% Americans consumed a diet, which was deficient for vitamins and minerals [15], [17]. The NHANES 3 study reported that multi-nutrient deficiencies were more prevalent in those with a BMI in the obese range than in the normal population [18], [19], [20], [21]. In the present review we will examine the role of thiamine, an essential component in the metabolism of glucose, in patients with obesity.

1.1. Search strategy and methodology