The 2025-2030 Dietary Guidelines for Americans (DGA), released in January 2026, further energized a marketplace already booming with protein reformulation. At the same time, “fibermaxxing” continues to gain traction online, while protein and fiber remain central to conversations around emerging obesity interventions like GLP-1-based medications. As consumers “max out” on macronutrients, there are opportunities to understand what higher intake levels mean for health.
For the consumer that looks for “protein in everything”— from ultra-filtered dairy products to protein-fortified chips —these trends bring new questions: Is there a level at which high protein intake begins to impact health in negative ways? Some protein is fermented in the gut. Fiber is likewise active there. Can any adverse effects of high protein in the diet be mitigated by increased fiber intake? Should dietary advice around fiber be different or targeted for consumers that choose to “protein max”? While authoritative dietary recommendations for both nutrients exist, the social and scientific discourse is challenging assumptions and motivating updates.
Protein plus
It is widely acknowledged that the revised DGAs suggest an amount of dietary protein higher than the current Recommended Dietary Allowance (RDA) (1.2-1.6 g/kg body weight versus 0.8 g/kg body weight, per day). Experts note that the higher values target different endpoints and health goals, so may not be ideal for “everyone” (which can be a point of confusion).
At the 2026 IAFNS Summer Science Symposium, researchers noted that the higher protein intake range was identified specifically as it relates to weight management. Although adverse effects of higher protein intake in healthy individuals are not well documented, speakers noted some data suggesting negative effects of high protein intake on longevity (aka lifespan), albeit from animal studies.
There are opportunities to learn more about how much protein is too much and whether higher intake provides any benefit for sedentary individuals—which most Americans are. It is worth noting that higher levels may still fall within the acceptable range for protein intake (Acceptable Macronutrient Distribution Range) set in 2005.
Interestingly, a 2016 position paper from the Academy of Nutrition and Dietetics, Dietitians of Canada and the American College of Sports Medicine (Thomas et al. 2016) recommended protein intake of 1.2–2 g/kg body weight “to support metabolic adaptation, repair, remodeling, and for protein turnover” in athletes, noting that “higher intakes may be indicated for short periods during intensified training or when reducing energy intake.” This adds to the discussion point that the “right amount” of protein depends on the individual’s lifestyle and health goals.
On the other side, the concept that increased protein may have negative implications for gut health is not new. Although protein absorption can be quite efficient, some amount of dietary protein reaches the lower gastrointestinal tract (GI). The lower GI is where dietary components come into contact with microbes and can be further digested by these bugs. It follows that the amount of protein that reaches the lower GI may increase as dietary protein increases overall. The modern diet may also include novel protein sources such as those added to bars and smoothies—these forms of protein may operate differently in the digestive process in ways that merit investigation.
Metabolites with implications
Why does it matter if protein reaches the lower GI tract? Protein fermentation by microbes can produce various metabolites with implications for health and disease. Several of these metabolites have been linked with inflammatory responses, tissue permeability or colitis severity, as examples (Diether and Willing, 2019; Yao et al. 2015). At the same time, much of this evidence is from in vitro or animal studies so what happens in humans is less clear (Windey et al. 2011, Wu et al. 2022). The absence of data, however, is not documentation of no harm.
Where does fiber fit in here? From a dietary perspective, when something goes up, something else must come down. It makes sense that the higher one’s protein intake—particularly from animal sources—the lower fiber intake might be. This tradeoff becomes apparent when examining US dietary intake data (Hoy et al. 2023): As protein intake increases in the diet, more people fail to meet recommended fiber intake.
The Gap
Regardless of protein intake, fiber intake is so notoriously poor in the US population that it has its own name (the “Fiber Gap”). Science supports some key benefits of fiber, with several specific fibers approved by the FDA as having specific “physiological effects of benefit to human health.” Despite dietary guidance to increase intake of fruits, vegetables and whole grains, and the availability of products fortified with FDA-approved fibers, the “gap” remains.
The gap is based on the recommended intake level, which hinges on the specific health benefit of reduction in cardiovascular disease risk (IOM, 2025). However, if other endpoints are explored, it is possible that a different or greater level of fiber intake would offer additional health benefits (see Morais Junior et al. 2026).
Looking Ahead
Looking into the future, what would be the optimal balance of these nutrients in a diet? Since gut microbes preferentially ferment carbohydrates over protein (Oliphant and Allen-Vercoe, 2019), adequate fiber intake gives microbes something else to work with first. That is likely why the same amount of protein in a meal can behave differently depending on what else is on the plate. Fiber fermentation produces many beneficial products, for example, short-chain fatty acids, B vitamins, neurotransmitters, and other compounds, although specific links to health outcomes are difficult to establish.
The national recommended intake amounts (Dietary Reference Intakes or DRIs) for protein and carbohydrates (which include fiber) are in need of an update. Over 20 years of additional science has been produced since the DRIs for macronutrients were first released. Since then, the importance of dietary patterns, individual response, food matrix, and other nuances have been elevated as relevant to comprehensive dietary guidance.
Diet trends and options have covered the gamut: low carbohydrate, high protein, low fat, vegan, plant-based, carnivore, and whatever is next. One thing we have learned is that nutrients impact biology and health in concert, not in isolation. It should be no surprise that increasing dietary protein may come at the expense of other macronutrient benefits.
Is there a place for specialized fiber intake guidance for individuals that choose to follow a high-protein diet? Given the intersecting roles of protein and fiber in health, and specifically in the gut, should they be considered together? At IAFNS, we see opportunities for clarifying how the trends of increased protein and fiber intake impact health and look forward to supporting more discussion and discovery to optimize individualized dietary guidance where needed.
Marie Latulippe is Senior Director of Science Programs at the Institute for the Advancement of Food & Nutrition Sciences. Marie works with several Nutrition Committees, manages the Board Program Committee and the Scientific Leadership Council and supports the Emerging Science process.
