Lost in the chaos of internet macronutrient recommendations, calculators, and one-size fits all diet plans is the potential existence of differences in nutrient needs between genders. And I’m not just talking about men needing more calories because they have an average larger body size than women. I’m talking about examining the potential difference in nutrient needs between genders due to hormonal and cellular machinery differences.
It turns out that arguably the most feared nutrient – fat – may be what women need to be eating more of. Well, if they want to improve their exercise performance, that is. Significant research exists that strongly suggests women rely on fat for fuel more-so than carbohydrates during low- and high-intensity exercise than men.
So, if you need more reason to grab another handful of almonds, the proof is in the high-fat, peanut butter pudding below!
1. WOMEN BURN MORE FAT AS FUEL THAN MEN
Your body relies on both carbohydrates and fat as fuel. Both are used as fuel sources at any given time, however, the preference for one source over the other depends on your activity level; the more active you are, or intense your exercise is, the more your body relies on carbohydrates for fuel. Conversely, the less active, or lower the intensity of your exercise, the more your body relies on fat for fuel.
The uniqueness of this relationship can be measured by looking at your respiratory exchange ratio (RER), which measures the amount of carbon dioxide you produce and the amount of oxygen you use at any given time. A higher RER (on a scale of 0 to 1.0) indicates greater reliance on carbohydrates whereas a lower RER (usually near 0.7) indicates a greater reliance on fat as fuel. A RER value of 0.85 is considered a near equal mix of reliance on carbs and fat.
Graphic: This chart describes the estimated percent of fuel usage from both carbohydrates and fat at various RER measures
Compared to men, women have a lower RER following both low and high-intensity exercise, demonstrating that their bodies rely more on fat. 1 And this makes sense when you consider that a study published in Journal of Neurological Sciences observed a 15 – 32% reduction in the activity of the enzymes responsible for the breakdown of stored carbohydrates (glycogen) into usable energy (glucose) during high-intensity exercise in women compared to men.2
2. WOMEN HAVE GREATER INTRA-MUSCULAR FAT STORES
You store fat in both fat cells (adipocytes) and within your muscle fibers (intra-muscular triglycerides). As exercise intensity increases, the amount of fat being used as fuel from adipocytes decreases and the amount of fat being used as fuel from intra-muscular stores increases.
A study published in the American Journal of Physiology Endocrinology and Metabolism found that women rely more on intra-muscular triglycerides for fuel during high-intensity exercise compared to men, which suggests they have a greater need for fat to push through such exercise.3 Furthermore, a study published in the European Journal of Applied Physiology and Occupational Physiology noted that women have a larger storage depot for intra-muscular triglycerides compared to men, which further supports an increased need for women to consume adequate amounts of fat.4
If you want to learn more about how you can optimize your health, physique, and performance by perfecting your fat sources, timing, and total intake, then you’ll love my online video course, “Everything You Need To Know About Fats!”
HOW MUCH FAT SHOULD WOMEN EAT?
More research is necessary to definitively state that women need more fat than men (on average), but so far, this much is clear: Women are not only well equipped to handle dietary fat, but also store more fat in their muscles compared to men and have the cellular machinery and hormones to support enhanced mobilization and use of fat during exercise. Failing to eat enough fat may jeopardize health, energy, and performance, and also impair menstrual cycle regularity, which further impacts the aforementioned consequences.
Although no specific recommendations for women exist at this time, a minimum starting point is targeting at least 20 percent of total calories from healthy fat sources each day. That’s 44 grams per day if you’re calorie goal is 2,000.
- Kendrick, Z.V. & Ellis, G.S. (1991). Effect of estradiol on tissue glycogen metabolism and lipid availability in exercised male rats. Journal of Applied Physiology, 71, 1694-1699.
- Green, H. J., Fraser, I. G. & Ranney, D. A. (1984). Male and female differences in enzyme activities of energy metabolism in vastus lateralis muscle. Journal of the neurological sciences, 65(3), 323-331.
- Steffensen, C.H, Roepstorff, C., Madsen, M. et al. (2002). Myocellular triacylglycerol breakdown in females but not in males during exercise. American Journal of Physiology Endocrinology and Metabolism, 282, E634–E642.
- Essen‐Gustavsson, B. & Tesch, P.A. (1990). Glycogen and triglyceride utilization in relation to muscle metabolic characteristics in men performing heavy‐resistance exercise. European Journal of Applied Physiology and Occupational Physiology, 61, 5-10.