There are four major types of RS (RS1-RS4), each of which contains specific chemical properties that render it resistant to digestion [9]. For example, RS1, found in whole grains and pasta with durum, contains a protein matrix which hinders its digestibility. RS2, found in common foods such as uncooked potatoes and unripe bananas, are resistant to carbohydrases until ripening or cooking. RS3 develops in starchy foods after storage because of the formation of double helices that render it resistant to enzymatic binding. RS4 is a chemically modified starch that resists enzymatic hydrolysis. To date, RS2 has received most of the attention for its beneficial metabolic properties [1]. However, RS4 was recently shown to reduce body weight more than RS2 in a murine model of obesity [10]. RS4 also increased resting energy expenditure and fat utilization compared to a waxy maize control in lean men after a single test meal [11]. Thus, RS4 represents an understudied form of RS that may beneficially affect human obesity and its comorbidities.
Increasing protein intake above commonly recommended levels is another dietary strategy that has been advocated for weight control and obesity prevention [12]. Similar to RS4, the effects of high protein diets are mediated, at least in part, through enhancing satiety and energy expenditure [13]. We recently demonstrated that increasing protein consumption to 35 % of total daily intake for eight weeks improved body composition and increased energy expenditure in obese adults [14].