How Exercise Affects Women’s Metabolism Differently From Men’s
How exercise affects a woman’s physique is one of the most misunderstood areas of physiology. Sure, more and more coaches and scientists are spreading the facts about the effect of different types of training on female metabolism, but stereotypes and misconceptions are still the norm.
This article will set the record straight and provide 7 facts so you can understand the different metabolic effects of exercise for women.
Fact #1: Women burn more glucose (carbohydrates) for energy at rest but burn more fat during exercise than men.
At rest women burn more glucose and less fat than men. In general, sedentary women are going to always favor the use of glucose for energy, making it harder to lose fat.
Fortunately, during exercise, women actually get a greater amount of energy from body fat than men do. This means that exercise is a catalyst for women to improve their bodies’ overall ability to call on fat for fuel, and it makes them more metabolically flexible.
Practical Application: If you are a woman who wants to lose body fat, exercise is essential to improve your body’s ability to use fat for energy.
Fact #2: Body fat distribution is different in women from men & this has a large effect on how their bodies respond when they try to lose fat.
Women store more fat right below the skin (subcutaneously), whereas men have more of the dangerous visceral belly fat. Visceral fat is metabolically active in a negative way and it reduces insulin sensitivity and makes the body less able to use blood sugar.
Women also have more fat in the lower body, particularly in the hip and thigh region, which has a protective effect. Lower body fat is actually “good” for women’s health, but to the chagrin of many women, it’s much harder to lose than fat located in other areas of the body.
That’s because fat cells in the hip and thigh region have more alpha receptors, which inhibit fat burning. Abdominal fat, on the other hand, tends to have more beta-receptors, which are more sensitive to fat burning.
This doesn’t mean that women can’t lose excess body fat from the hip and thigh region, but they will have better results with targeted training and smart nutrition. Interestingly, although hip-thigh fat cells tend to have more alpha receptors, beta receptors are also present, and the trick is to stimulate these cells with the hormone epinephrine, which has been shown to lead to fat loss.
Practical Application: Lift weights and do interval training to increase muscle mass for a higher metabolism if you want to lose fat.
Factors that reduce or eliminate the benefit of training include using loads that are too light, not increasing the weight progressively, or not doing enough work (too low of a volume). Being sedentary is also bad news.
Fact #3: Women tend to have better metabolic health despite having less muscle mass.
Muscle tissue consumes the majority of the glucose transported in the blood (70 to 90 percent), which is one reason that the more muscle you have, the better your metabolic health will be and the easier it will be to lose body fat.
This is a well-established fact when you compare people of the same sex who have different body compositions. For example, for every 10 percent increase in muscle mass that a woman has, there is an 11 percent increase in insulin sensitivity, which is the ability of your cells to bind with insulin to burn blood sugar for energy. The same goes when you compare men.
But there’s a strange paradox when you compare metabolic health between men and women. Although women tend to have about 70 percent of the muscle mass and double the body fat as men, they have significantly better blood sugar tolerance.
This is partly because women have higher estrogen levels than men, which improve the body’s ability to burn carbs. For example, during the follicular phase of a woman’s cycle when estrogen levels peak, glucose clearance in muscle is at its highest.
Practical Application: Carbs are your friend—just be smart about which ones and when you eat them. Go higher on carbs after workouts and especially on intense training days.
Try increasing carbs to sync with your cycle: Go higher in carbs from the start of your period until ovulation—generally the first 14 days—because insulin sensitivity is higher. Eat more protein and low-carb foods for the two weeks before your period.
Fact #4: Women respond differently to high-intensity training compared to men.
Women rely more on aerobic pathways for energy production whereas men rely more on anaerobic pathways. A number of factors contribute to the difference:
Women have more type 1 muscle fibers, which are better suited to aerobic exercise.
The fact that women burn more fat during exercise contributes because fat is a slower burning fuel source than carbs.
Women have a lower rate of force development and reduced power output because they use the stretch-shortening cycle differently than men.
However, one area that women come out on top is in regards to recovery. Studies show that women don’t require as much rest between intense burst of exercise, and they don’t experience as much drop off in power and speed as a workout progresses.
In addition, a sprint interval study found that trained women had much higher heart rate maximum values than men, indicating that women may push themselves harder due to an accelerated recovery between work intervals.
Practical Application: To achieve the optimal dose of overload, women will need shorter rest periods than men when weight training. An example from the research shows that for interval training with work intervals of 1 minute or longer, a 2:1 work-to-rest ratio should provide adequate recovery.
Fact #5: Hormones play an important role in shaping body composition in women, but not in the way most people think.
A common misunderstanding is that women can’t build as much muscle as men because they don’t have as much testosterone. In fact, women and men have equal ability to gain strength and muscle from training as men because the two most influential factors—protein synthesis and gene signaling—are nearly equal between the sexes.
However, women start out with less muscle and their bodies tend to be lighter and smaller than men’s, so a 10 percent increase in muscle for a woman will be smaller in absolute terms.
In addition, very large increases in testosterone, such as when a male goes through puberty or when one takes testosterone in the form of steroids, will increase muscle and strength.
The small, transient post-workout increase that men experience doesn’t appear to influence muscle growth. Rather, the exercise-induced increase is thought to be linked to athletic performance. A woman who is closer to the upper limit of her testosterone threshold may have an advantage over other women in developing strength.
Practical Application: If you’re a woman who wants to put on muscle, you’re in luck! You won’t look like a man, but you will be able to build muscle in the same way men can if you train to maximize protein synthesis and related muscle building factors.
Fact #6: The most important hormones for female body composition are growth hormone and estrogen.
It’s likely that one of the most important factors for body composition in women is their higher release of growth hormone (GH) in response to exercise.
In order to burn fat you need a couple of things happening in your body at the same time: Insulin needs to be low, and a key fat burning enzyme, Hormone Sensitive Lipase (HSL) needs to be elevated. An antagonist enzyme, Lipoprotein Lipase (LPL) needs to be low because LPL leads to fat storage.
Estrogen and growth hormone work together to create this environment. Estrogen stimulates GH and blocks LPL. GH inhibits insulin and triggers HSL release. Now, if you add the right type of exercise into the mix, you create the perfect situation for fat loss.
For instance, in a recent study, scientists showed that the killer all-out Wingate sprint, which is done for 30-seconds on a resisted cycle, led to GH levels in women that were double that of men. GH peaked much sooner in the women than in the men, but interestingly, lactate levels were lower, suggesting that aerobic pathways contributed to fuel the sprint in the women.
Practical Application: The deciding factor in how women’s bodies respond to exercise is in how you program your workouts. Make sure your work intervals are hard and that your rest intervals are long enough to allow you to sustain intensity for all your interval repeats, but not too long so that you waste time.
Fact #7: Women experience stress differently from men, which influences fat loss & workout recovery.
Anytime the human body is stressed, we experience an increase in the hormone cortisol. This happens to both men and women after exercise and when life gets rough.
Studies show that women experience stress differently from men in a couple of ways.
First, a series of studies show that in response to traditional weight training workouts women tend to have a lower cortisol response than men. However, after a high-intensity “extreme” weight workout that used a pyramid design (10 sets starting with 10 reps and decreasing 1 rep each set) and no rest between sets for the bench press, deadlift, and squat, women and men had similar sky high cortisol levels.
Cortisol was much higher than values reported on all previous research that used the same intensities (75 percent 1RM), primarily because those studies all used rest periods of 1 to 3 minutes. Cortisol was also higher than what has been recorded from high-intensity interval training and aerobic exercise.
The scientists expressed concern because women already have higher resting cortisol levels. Plus, there’s evidence that the cortisol receptors on muscle tissue are already saturated before the onset of intense training.
This has negative metabolic implications and could lead to a catabolic environment for women. You might lose muscle, cause persistent inflammation, and have a hard time recovering from workouts.
Practical Application: Doing crazy intense or extra long workouts will only defeat your purpose and lead to poor body composition.
In terms of rest periods during workouts, use them! You need to be able to maintain the prescribed intensity without compromising technique.