Foods that enhance satiety can help consumers to resist environmental cues to eat, and improve the nutritional quality of their diets. Viscosity generated by oat beta-glucan, influences gastrointestinal mechanisms that mediate satiety. Differences in the source, processing treatments, and interactions with other constituents in the food matrix affect the amount, solubility, molecular weight, and structure of the beta-glucan in products, which in turn influences the viscosity. This study examined the effect of two types of oatmeal and an oat-based ready-to-eat breakfast cereal (RTEC) on appetite, and assessed differences in meal viscosity and beta-glucan characteristics among the cereals.
Forty-eight individuals were enrolled in a randomized crossover trial. Subjects consumed isocaloric breakfast meals containing instant oatmeal (IO), old-fashioned oatmeal (SO) or RTEC in random order at least a week apart. Each breakfast meal contained 218 kcal (150 kcal cereal, and 68 kcal milk) Visual analogue scales measuring appetite were completed before breakfast, and over four hours, following the meal. Starch digestion kinetics, meal viscosities, and beta-glucan characteristics for each meal were determined. Appetite responses were analyzed by area under the curve. Mixed models were used to analyze response changes over time.
IO increased fullness (p = 0.04), suppressed desire to eat (p = 0.01) and reduced prospective intake (p < 0.01) more than the RTEC over four hours, and consistently at the 60 minute time-point. SO reduced prospective intake (p = 0.04) more than the RTEC. Hunger scores were not significantly different except that IO reduced hunger more than the RTEC at the 60 minute time-point. IO and SO had higher beta-glucan content, molecular weight, gastric viscosity, and larger hydration spheres than the RTEC, and IO had greater viscosity after oral and initial gastric digestion (initial viscosity) than the RTEC.
IO and SO improved appetite control over four hours compared to RTEC. Initial viscosity of oatmeal may be especially important for reducing appetite.
Alex’s Notes: If you recall back to May 13th, I talked about a meta-analysis on the beneficial effects of oat intake on glycemic control and insulin in both healthy and diabetic individuals. On that note, a recently published study in the Nutrition Journal continues to provide support for oatmeal consumption. The US will have a projected 65 million more obese adults in 2030 compared to 2010, but there is hope in the consumption of fiber-rich foods for long-term weight reduction. One very special fiber is beta-glucan, which forms a viscous solution when mixed with liquids that acts to delay digestive transit time, increase stomach distention, and increase the absorption of some nutrients. And guess what plant has significant amounts of beta-glucan… oats! Of course, the processing of oats affects numerous properties of the beta-glucan, so the study at hand had two goals: to measure the satiety of oats compared to breakfast cereal, and see how each oat breakfast’s effect differed based on the type of oat processing.
Importantly, this study was conducted in 48 healthy subjects (average age 30 years) that varied in BMI. Three were underweight, 22 normal weight, nine overweight, and 14 obese. The two oat breakfast meals were Quaker Instant Oatmeal (IO) and Quaker Old Fashioned Oatmeal (SO), while the breakfast cereal was Honey Nut Cheerios (RTEC). The meals were consumed after an overnight fast of ten hours, with no alcohol or exercise for 24 hours prior.
The results were most interesting. IO consumption increased fullness, suppressed desire to eat, and reduced prospective intake more than the RTEC over the entire four-hour period and consistently at the 60-minute mark, but the SO only reduced prospective intake more than the RTEC and no other satiety measure. In other words, the more processed instant oats are more satiating than the rolled oats. Why?
It turns out that satiety depends on the meal’s initial viscosity. Indeed, the more satiating IO were also shown to have greater initial and subsequent viscosities compare to RTEC, whereas SO only had greater subsequent viscosity compared to RTEC. This is likely due to IO being composed of thinly cut flakes that are able to hydrate more easily from the added water than the thicker cut SO.
So how much oatmeal should you eat? Well, one study concluded that the optimal dose of beta-glucan affecting satiety and other markers of appetite regulation were between 4-6 grams, although other studies have found benefits in a dose-dependent manner starting with as little as 2.2 grams. Given one standard serving of oats is 3-5 grams of beta-glucan, I would say that is sufficient for the benefits.