By Aaron Finn (Msc Sport and Exercise Nutrition)
Do males and females lose the same amount of body fat if they are put into the same calorie deficit?
Does it take the same amount of time for females to lose the same amount of body fat as men?
In today’s blog, I am going to share with you how the physiological differences between males and females can determine the different rates at which they lose weight.
By reaching the end of this blog you will understand:
- How to effectively drop weight.
- How the physiological differences in male and females can affect weight loss/ weight gain.
- How to use this information as a female athlete to optimize weight changes.
How does weight loss occur?
Weight fluctuations are determined by the type of imbalances that occur between energy intake and energy expenditure.
Energy Intake: is the energy/caloric content of any food/drink ingested over a period of time. For example, an athlete may have a daily energy intake of 3,000 calories per day, calculated by the food/drink they ingest.
Energy expenditure: is the energy used to support the body’s daily functions and activities. It is broken up into 4 categories:
- Exercise activity thermogenesis involves the energy needed to support exercise and sport, surprisingly this only represents 10% of total energy expenditure! You can calculate this by estimating your PAL LiveLighter – Physical Activity Calculator.
- The thermic effect of food involves the energy needed to break down food ingested. You can find this by multiplying your BMR by 0.1 to find how many calories are burned when breaking down food in the body. E.G 1,600 x 0.1 = 160 calories.
- Non-exercise activity thermogenesis involves the energy needed to complete non-exercise activities such as walking to the shop or gardening. You can calculate this by estimating your METS. Calories Burned/METs Calculator
- Basal metabolic rate is the energy needed to support daily bodily functioning such as breathing, circulation, and cognitive functioning. You can calculate this by choosing one of many of scientific formulas such as BMR calculator for Athletes – The Endurance Edge. Be sure to ask your nutritionist which formula is best for you.
All these factors play a part in determining how much energy is expended per day.
Once total energy expenditure has been calculated, you can now find your maintenance, surplus, and deficit calories.
If you do not meet your energy expenditure needs each day for some time, you will experience weight loss. Similarly, if you exceed your energy expenditure needs you will gain weight. Lastly, if you meet your needs each day, your weight will remain the same.
Weight loss is as simple as that. Every fad diet you know follows this same concept of the calorie deficit, they just achieve it in different ways.
For example, intermittent fasting is just choosing which time of the day is easier for you to restrict calories so that at the end of the day your calories will be in a deficit.
Similarly, veganism and vegetarian diets typically involve more nutrient-dense foods in comparison to calorie-dense foods. Which ultimately leads to lower calories.
There we have it, the concept of weight loss is much simpler than most companies and professionals have led us to believe…
BUT (there’s always a but)
There are physiological differences between males and females that affect the rate at which this weight loss occurs.
Weight Fluctuations for Females vs Males
As mentioned in our other blogs, the menstrual cycle can have significant effects on performance in female athletes. It is typically divided up into 4 sections:
- The Follicular Phase
- The Ovulatory Phase
- The Luteal Phase
Each phase presents its own enhancers and/or diminishers for performance. For example, menstruation may impact performance negatively due to fatigue/menstrual cramps. Similarly, ovulation may impact performance positively due to increased strength capacity due to increased levels of testosterone.
In the same way that each phase affects performance, for some females, it likely affects weight measurements. Your physiology changes in each phase. Some phases can increase factors such as water retention, carbohydrate loading, fat oxidation etc.
Some females take measurements such as weight and circumferences as regularly as daily or once per week. With so many fluctuations in physiology each week, you may blame your weight gain/loss on yourself, when in reality it may be due to physiological reasons such as water retention caused by the hormonal fluctuations of the menstrual cycle.
It takes around 33% longer for females to burn the same number of calories as males. This is an important fact to consider as an athlete/coach. Women are not smaller men. The physiologies are very different.
Pre-menstrual cravings are a well-known symptom of pre-menstrual syndrome for many females. Did you this happens because your metabolism increases during the luteal phase?
Each female burns anywhere between 1 and 300 extra calories each day during this time. This basically means that the rate at which you break down food increases during this time, and your body craves more food to match your energy needs. This is why you crave calorie-dense foods such as chocolate, crisps, and takeaways!
This is an important fact to consider when beginning a weight loss journey. Females have been found to consume 500 extra calories during this time to due cravings. Although this may not seem like a lot, this could tip the balance of needs to a calorie surplus, and over time this can lead to weight gain!
How should you use this information as a female athlete to optimize weight changes?
Let’s begin with taking measurements to assess weight fluctuations throughout the hormonal changes that occur during the menstrual cycle.
Given that each stage may affect weight results, weight measurements should be compared from stage to stage. For example, measurements taken during the luteal phase should be compared to the next luteal stage measurements.
To combat binge eating during luteal phases, try to allocate extra calories during this time, and try to implement higher volumes of nutrient-dense foods.
For female athletes in heterosexual relationships, it’s important to remember that eating the same as your partner, and exercising for the same amount of time as your partner will not result in the same weight loss.
This does not mean you have to constantly restrict food with your partner but is something to consider.
Take Home Message
- Weight loss is achieved by having a higher energy expenditure in comparison to energy intake, and vice versa with weight gain.
- The physiological differences between males and females can affect the rate at which they lose weight.
- Weight measurements may fluctuate between stages of the menstrual cycle due to factors such as water retention. Therefore, weight measurements should be compared from stage to stage instead of week to week.
- Metabolism speeds up during the luteal phase and females can burn anywhere between 1 and 300 extra calories per day.
- This can lead to cravings and extra calories being consumed, leading to a calorie surplus. To combat binge eating during this time, extra calories could be allocated as well as more nutrient-dense foods.
- Benton, M. J., Hutchins, A. M., & Dawes, J. J. (2020). Effect of menstrual cycle on resting metabolism: A systematic review and meta-analysis. PloS one, 15(7), e0236025. https://doi.org/10.1371/journal.pone.0236025
- Cohen, I. T., Sherwin, B. B., & Fleming, A. S. (1987). Food cravings, mood, and the menstrual cycle. Hormones and behavior, 21(4), 457–470. https://doi.org/10.1016/0018-506x(87)90004-3
- Gorczyca, A. M., Sjaarda, L. A., Mitchell, E. M., Perkins, N. J., Schliep, K. C., Wactawski-Wende, J., & Mumford, S. L. (2016). Changes in macronutrient, micronutrient, and food group intakes throughout the menstrual cycle in healthy, premenopausal women. European journal of nutrition, 55(3), 1181–1188. https://doi.org/10.1007/s00394-015-0931-0
- Oosthuyse, T., & Bosch, A. N. (2010). The effect of the menstrual cycle on exercise metabolism: implications for exercise performance in eumenorrhoeic women. Sports medicine (Auckland, N.Z.), 40(3), 207–227. https://doi.org/10.2165/11317090-000000000-00000