Before I go any further, let me just define terms here. Resistant starch is starch that your body cannot absorb. It therefore passes through the digestive tract and out into fecal waste without significant entry into the body, but in so doing it provides food for intestinal microbes, and therefore has been demonstrated to support a healthier and more diverse microbiome. Some natural sources of resistant starch include whole grains, potatoes, beans, and unripened fruit. By contrast, non-resistant starch is starch that your body absorbs and quickly converts into sugar for energy. Common sources of non-resistant starch include breads and pasta.
Here, rather than feed people foods that contained resistant or non-resistant starch, the researchers gave a supplement with each meal. Other than being told to follow a common sense diet, no other intervention was taken, and the subjects otherwise kept eating as per usual. Most importantly, there were no major differences between the two groups in terms of what they ate – the researchers determined that both groups averaged the same amounts of calories, protein, fats, and so forth. Likewise there were no other significant differences between the two groups such as exercise habits, alcohol use, or anything else that might reasonably be expected to affect body weight or liver health.
The results were profound. At the end of the four months, the group receiving the resistant-starch supplement:
Weighed less
Had less liver fat and visceral fat
Had lower blood pressure
Had better blood sugar control
Had less insulin resistance
Had improvements in cholesterol and triglyceride levels
In other words, with no effort other than taking a few tablespoons per day of a starch supplement, the experimental group lost weight and became more metabolically healthy. Moreover, the researchers took the additional step of trying to figure out exactly how to explain this difference. They analyzed the microbiome of both groups, and found that the group taking the resistant starch had significant improvements in their microbiome composition.
Then they went so far as to transplant stool samples from both groups into lab mice and were able to document that the mice receiving samples from the resistant starch group also experienced many of the same health improvements such as a reduction in body fat and liver fat, thus providing a strong piece of evidence that the health benefits the humans in the study experienced were due to the microbiome changes.
Putting this all together, it appears that simply increasing resistant starch consumption, absent any other changes, can lead to improvements in the gut microbiome that, in turn, lead to weight loss and improved metabolic health.
One actionable takeaway from this study would be to try to increase your consumption of foods high in resistant starch. A good tip regarding this is that resistant starch tends to increase when foods that are naturally high in them such as potatoes, rice, or oats are allowed to cool. So for example boiling or steaming potatoes and then refrigerating them and eating them as a salad rather than when they are hot off the stove would be a good way to get more resistant starch.
Another option would be to re-create the experiment in your own life, and take a resistant starch supplement before each meal for a few months. The specific type of supplement used in the study was called “Hi Maize 260” which is a corn-derived product. Unfortunately it doesn’t seem to be widely available in the commercial market here in the United States. However, it’s probable, though not definitely proven, that other forms of resistant starch supplements (e.g. green banana powder) would have similar benefits.
Finally, good studies tend to fit into the bigger picture of what we already know, and this study hits the mark well in this area. Consider:
Does a lot of evidence suggest that, compared to the standard American diet, a diet that increases the intake of whole grains, legumes, and vegetables is likely to be more healthy? It certainly does. This study provides a piece of evidence that helps to explain why that may be so.
Does a lot of evidence suggest that, compared to the standard American diet, a very low-carb or even keto type diet can lead to weight loss and better health? It certainly does. This study supports that too, by demonstrating that diets high in non-resistant starch such as bread, pastry, and pasta, can be associated with more abdominal fat, and hence providing a piece of evidcence for why restricting such foods can lead to weight loss.
Does a lot of evidence suggest that having a healthy gut microbiome has downstream health effects that are very beneficial? It certainly does. This study is a good demonstration of how a person can “hack” their microbiome in the real world to lead to body composition and health improvements.
Finally, let me point out two things that are themes I return to a lot on this blog. First, this blog is just for informational purposes and does not constitute medical care. You should discuss any specific changes you plan to make with your own healthcare practitioner. And secondly, the downsides of taking resistant starch are likely to be minimal if any, so even if this supplement only works a bit, it’s probably low-risk to give it a try.
