Potatoes seem to get a bad rap because of their high glycemic index. But it turns out that they have little fat and low energy density. When potatoes are cooked and then cooled, you get slowly digested starch, aka resistant starch type 3.
Resistant starch type 3 is a type of starch that is not easily digested in the small intestine, but rather ferments in the large intestine. This process can produce beneficial compounds that promote gut health and may also lead to lower blood glucose levels.
Beans are a powerhouse that is linked with reduced insulin resistance and weight loss. They also contain resistant starch type 3. In a new study, researchers wanted to see if potatoes could be substituted for beans and provide similar benefits of weight loss and reduced insulin resistance.
In the study published in the Journal of Medicinal Food, researchers randomized 36 participants, ages 18-60, with insulin resistance to 8 weeks of a low energy–density diet (1 kcal/g) based on potatoes or beans. The starting body mass index of the participants ranged from 25-40 kg/m2. Insulin resistance was defined as a HOMA-IR score of greater than 2.
HOMA-IR stands for homeostatic model assessment of insulin resistance. It is calculated by using fasting insulin and fasting glucose levels. The formula is:
· HOMA-IR = (fasting insulin x fasting glucose) / 22.5
The resulting score provides an estimate of insulin resistance. Typically, a score of 1.0 or lower is considered normal, with higher scores indicating greater insulin resistance. It's important to note that while HOMA-IR is a useful tool for assessing insulin resistance, it is not a perfect measure and may not be accurate in all situations. Other factors, such as obesity, physical inactivity, and certain medications, can also affect insulin resistance.
The participants in the study were given a controlled diet consisting of 50%-55% carbohydrates, 30%-35% fats, and 15%-20% protein. Each meal in the potato group included a side of potatoes, while each meal in the bean group included a side of beans.
The researchers evaluated two outcomes: the mean change in blood glucose concentration and weight loss. Fourteen individuals in the potato group and 17 in the bean group completed the study. However, the data from all 18 individuals in each group were included in an intent-to-treat analysis.
The study completers in the bean group showed an average decrease of 1.4 in HOMA-IR from baseline (P = .02), while a similar decrease of 1.3 was observed in the potato group (P < .05). There was no significant difference between the two diets in terms of the decrease in HOMA-IR.
Both groups in the study were compliant with their assigned diets about 88% of the time. Over the study period, the participants in both groups lost weight, with the average weight reduction being 5.82 kg in the potato group and 4.0 kg in the bean group. Both groups also showed a significant decrease in their BMI, with the potato group having a greater reduction (2.04 kg/m2) compared to the bean group (1.35 kg/m2).
Although there were no significant differences in baseline BMI, the researchers noted that the reduction in BMI was higher at baseline and had a greater reduction in the potato group compared to the bean group. There was no significant difference between the two groups in terms of blood glucose response, nor was there any significant difference in blood glucose response from baseline in either group.
For consumers, the main takeaway from this study is that eating a small portion of potato as part of a balanced, low-calorie diet did not have any negative effects on glucose or insulin when compared to a diet of beans. It's important to note that this was a very small study that only lasted for a short period of time, but the results suggest that consuming potatoes in moderation as part of a balanced diet is unlikely to cause any adverse effects on blood sugar or insulin levels
Candida J. Rebello, Robbie A. Beyl, Frank L. Greenway, Kelly C. Atteberry, Kristin K. Hoddy, and John P. Kirwan.Low-Energy Dense Potato- and Bean-Based Diets Reduce Body Weight and Insulin Resistance: A Randomized, Feeding, Equivalence Trial.Journal of Medicinal Food.Dec 2022.1155-1163.http://doi.org/10.1089/jmf.2022.0072