High Carb After Keto: Why Starch Might Be Worse Than Sugar
A new study shows switching from low-carb to high-carb increases inflammation, but only if the carbs are refined starch, not sugar.
Based on coverage by ScienceAlert
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You lose 15 percent of your body weight on a strict keto diet, then you go back to eating pasta and bread. A new study from NYU Langone Health suggests the aftermath isn't pretty if you load up on refined starch.
Low-carb diets are tough to stick with long term. People hit their goals and slip back into old habits. This study, published in Cell Reports, looked at exactly what happens to the body during that switch. The results challenge the idea that all carbohydrates are created equal.
the study details
A team led by researchers at NYU Langone Health ran a controlled feeding experiment. They started with 54 participants aged 18 to 50 who were overweight or obese but did not have cardiovascular disease or diabetes.
The process was rigorous. Everyone had to go through a run-in phase on a very-low-carb diet designed to produce a substantial 40 percent calorie deficit. This phase helped them lose about 15 percent of their weight. Once they hit that mark, the real test began. Participants were randomly assigned to one of three groups for 10 weeks.
One group stayed on the low-carb diet. The other two groups switched to high-carb diets with the same macronutrient balance (57 percent carbohydrate, 25 percent fat, 18 percent protein). The difference lay in the source of those carbohydrates. One group received 20 percent of their total energy from starch in refined grains. The other group received the same proportion from added sugar.
why starch triggers inflammation
Blood test analyses from about 40 participants showed that the high-starch diet triggered signs of increased inflammation compared to the other two groups. The researchers saw higher levels of adipsin, a signaling protein linked to inflammation. They also found increased signs of activation in immune cells, including CD4+ T cells and neutrophils.
The high-sugar group actually scored the lowest of all three groups in terms of immune activation. I did not expect the sugar group to look better than the starch group, but that is what the data showed.
The researchers noted that this reduction in inflammatory pathways in the high-sugar group should not be interpreted as an overall benefit of sucrose or fructose consumption. Suppressing complement-mediated immune responses could impair host defense and make it harder for your body to fight infections.
the mechanism behind the spike
Refined grains have been linked to markers of low-grade, chronic inflammation. One established mechanism is their ability to increase postprandial blood glucose levels, as quantified by the glycemic index.
Sharp rises in glucose can activate the immune system's complement system, which triggers further inflammatory pathways. This mechanism was also seen in mice. Animals fed maltodextrin, a starch derivative, after fasting showed increased immune activity. The type of carbohydrate matters more than the quantity when you are coming off a restrictive diet.
what this means for keto dieters
The study shows that when coming off a low-carb diet, the type of carbohydrate matters. Starch from refined grains appears to drive inflammation, whereas sugar did not show the same effect in this specific study.
If you plan to switch from a low-carb diet back to a higher carbohydrate intake, pay attention to the source. Starch-rich diets drive inflammation. Choosing complex carbohydrates over refined grains helps keep your system calm during the transition.
the caveats
This study proves only a small amount. It involved about 40 participants and lasted only 10 weeks, which might not capture the long-term effects of these diets in real life. The researchers acknowledge that physiological adaptation over time could change the results. This does not mean you can eat sugar, but it is a warning about processed grains.
Practical Takeaway: When reintroducing carbohydrates after a low-carb diet, prioritize complex carbs over refined starches to minimize inflammation triggers.
Keto Swaps From Our Kitchen
If this research has you rethinking refined starch, these are the swaps we actually cook - each one tested in our own kitchen.
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