Combining high-carb with high-fat in a single meal is hazardous to your health.
The Danger of Combining High-Carb and High-Fat in a Single Meal: A Comprehensive Look
In recent years, nutrition science has advanced our understanding of how different macronutrients—carbohydrates and fats—affect our health. While both high-carbohydrate (high-carb) and high-fat diets have their proponents, emerging research suggests that combining large amounts of both in a single meal may be more harmful than consuming either nutrient in isolation. This holds true even when fats come from typically “healthy” sources like nuts or avocado.
The Effects of a High-Carb, High-Fat Meal When high-carb and high-fat foods are consumed together in a large meal, the body enters a metabolic state where the negative effects of each macronutrient are amplified. Studies show that this combination can impair metabolic function, promote inflammation, and increase the risk of cardiovascular diseases, such as heart attack and stroke, as well as type 2 diabetes.
One reason is how the body processes these nutrients. Carbohydrate intake triggers insulin release to regulate blood sugar. Simultaneously, dietary fat enters the bloodstream and is processed by the liver or stored in fat cells. When both are present in excess, insulin becomes less effective—a phenomenon known as insulin resistance. A 2014 study in Diabetes Care found that high-fat, high-carb meals increase postprandial (after-meal) insulin resistance more than meals lower in both macronutrients (Buchleitner et al., 2014). The presence of fat blunts the insulin response, leading to blood sugar spikes and a heightened risk of diabetes.
This combination also contributes to lipotoxicity—a state in which excess fat and sugar overwhelm the liver, generating toxic byproducts that damage liver cells. A 2016 Hepatology study confirmed that high intakes of both macronutrients accelerate liver inflammation, a precursor to non-alcoholic fatty liver disease (NAFLD) (Cohen et al., 2016).
Inflammation and Cardiovascular Damage High-carb, high-fat meals can also trigger systemic inflammation and oxidative stress, key contributors to cardiovascular disease. Refined carbs, in particular, elevate pro-inflammatory cytokines. When combined with trans or saturated fats, the body’s inflammatory response is magnified. A 2015 study in the Journal of the American College of Cardiology found that such meals raised oxidative stress and inflammatory markers, promoting plaque buildup and arterial damage (Basu et al., 2015).
The Risk of Excess Fat—Even from “Healthy” Sources Even meals high in “healthy” fats, such as nuts or seeds, can cause harm when consumed in excess. Over 300 calories of fat in a single sitting can raise blood triglycerides and inflammatory markers. Research in The American Journal of Clinical Nutrition (2011) showed that high-fat meals—regardless of the fat source—temporarily impair vascular function and raise cardiovascular risk (Pischon et al., 2011).
A Lancet study (2016) reinforced that chronic overconsumption of fats—even unsaturated fats—can still increase oxidative stress, inflammation, and the risk of atherosclerosis (Kris-Etherton et al., 2016).
The Importance of Moderation and Food Combining Even plant-based fats and proteins (such as soy or pea protein powders) can be problematic in excess. Excessive protein, whether from animal or plant sources, places metabolic stress on the kidneys and liver and may increase inflammation and IGF-1 levels, a growth hormone linked to cancer risk. High-protein diets also suppress metabolism over time, especially in low-carb contexts, as discussed in this weight-loss article.
Moderation and strategic food combining are key. For meals high in complex carbs (e.g., more than 50% of total calories), keep fat intake to 10–20%. If you’re eating a high-fat food—such as a handful of nuts or a quarter of an avocado—consume it with a lower-carb meal or as a stand-alone snack. Avoid combining large amounts of both macronutrients at once.
Additionally, low-carb diets that emphasize high protein and fat intake often backfire. While they may promote initial weight loss, they reduce insulin sensitivity over time. When healthy carbs are reintroduced, the body handles glucose less efficiently, producing more insulin and storing more fat. This leads to rebound weight gain and a slowed metabolism over time, requiring ongoing calorie restriction to maintain weight loss.
The popular keto and low-carb diets actually INCREASE insulin resistance over time, because by avoiding healthy whole/complex carbohydrates, which is what your body and metabolism need for optimal health, your body becomes more insulin resitant and less sensitive to insulin, so that once you do finally introduce whole/healthy carbs back into your diet, you then have higher blood sugar hanging out in the blood stream longer, and thus more insulin produced and more fat storage, thanks to being less sensitive to insulin. Overtime this is what leads to insulin resistance and diabetes. This is why it's not a good idea to do low carb for long periods of time. And not a lot of people know this, but low carb actually DECREASES your metabolism, causing you to have to continually eat less and less over time, in order to avoid a weight-loss plateau. Read more about that on this weight-loss article here.
Evolutionary Perspective: A Natural Separation of Macronutrients From an evolutionary standpoint, humans rarely consumed large amounts of carbs and fats together. During the Ice Age and other prehistoric periods, food sources were limited. Our ancestors ate what was available—either fatty foods like nuts and seeds or starchy plants like tubers—but not both in one sitting. There’s no natural, unprocessed food that contains high amounts of both fat and carbohydrates together.
This supports the idea that combining large amounts of fat and carbs in one meal is unnatural—and only in the last 200 years has this become a common dietary pattern, particularly in processed and fast foods.
Final Thoughts The science is clear: combining high levels of both carbohydrates and fats in one meal can be metabolically harmful. Instead, aim for balanced, moderate meals, and avoid excessive fat or carb intake—especially together. Focus on whole, unprocessed foods and thoughtful portioning to support long-term health and metabolic efficiency.