Researchers Identify Sex-Based Differences In Diet and Metabolism

Breakfast is often described as the most important meal of the day. Although this is not a recent discovery, how men and women fuel their bodies after a long night of fasting could contribute to weight loss, emphasizing the effects of personalized eating habits rather than conforming to a “1 meal plan fits all” approach.¹

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Nutrition relies on carbohydrates, fats, and proteins, with the body preferentially using carbohydrates for energy to maintain stable blood glucose. However, when calorie intake exceeds the body’s needs, the excess energy is more readily stored as fat due to its higher energy density than carbohydrates.²

Sex is known to play a significant role in shaping overall metabolism, which is a biological distinction known as sexual dimorphism. This leads to adaptations in body composition, metabolic rates, how the body uses different energy sources, and hormonal control. Researchers note that these differences become apparent under various physiological states, including fasting, feeding, low blood sugar, and physical activity.²

Previous studies have shown that men favor carbohydrate metabolism, whereas women favor lipid metabolism. However, few of the mathematical models that assessed metabolism address the nuanced differences between male and female physiology. In a recent study, researchers created a mathematical model that introduces a sex-specific computer model of metabolism across multiple organs to simulate how different meals are processed. The study aims to quantify and evaluate sex differences in carbohydrate and fat use at the whole-body and organ levels.¹

Researchers conducted 4 experiments, directing participants to consume mixed meals after a 12- to 14-hour overnight fast, including 96 g of carbohydrates and 33 g of fat, 139 g of carbohydrates and 17 g of fat, 58 g of carbohydrates and 27.7 g of fat, and 289 g of carbohydrates and 45 g of fat. After consumption, the researchers evaluated the participants’ postprandial and postabsorptive states.¹

The results demonstrate no significant differences between men and women in glucose, insulin, or lactate responses but show heightened lipolytic responses among female models, which were verified by higher circulating free fatty acid and glycerol levels during fasting.¹

“Since women have more body fat on average than men, you would think that they would burn less fat for energy, but they don’t,” Anita Layton, PhD, a professor of applied mathematics at the University of Waterloo, said in a news release. “The results of the model suggest that women store more fat immediately after a meal but also burn more fat during a fast.”¹

Consuming a breakfast with a higher percentage of fats, such as omelets and avocados, could be more beneficial for women than men after a long fasting period. In contrast, men’s metabolisms demonstrate better responses to a meal with higher carbohydrates, such as oatmeal and pancakes. Keep this in mind next time you are perusing the diner breakfast menu.

REFERENCES

1. Should men and women eat different breakfasts to lose weight? News release. University of Waterloo. October 7, 2024. Accessed April 21, 2025. https://uwaterloo.ca/news/media/should-men-and-women-eat-different-breakfasts-lose-weight#:~:text=It's%20not%20a%20bad%20thing,help%20you%20lose%20some%20weight

2. Abo SMC, Layton AT. Modeling sex-specific whole-body metabolic responses to feeding and fasting. Comp Biol Med. 2024;181:109024. doi:10.1016/j.compbiomed.2024.109024