If you are biologically female and have ever approached a diet or weight-loss regimen with a male partner, you may have felt like the odds were stacked against you. Because of our physiological, structural, and (majorly) hormonal differences, male and female metabolic systems work very differently.
It can be frustrating, as a female, to watch as extra weight seems to easily fall off of some males with slight dietary or behavioral changes. Women are more likely to struggle and sacrifice to see less dramatic results. It’s not in your imagination. It’s science.
But resistance is not futile! In this article, we will explore how our bodies work differently so that we can make the appropriate behavioral and nutritional adjustments for our unique metabolic systems.
It is entirely possible for both men and women to reach and maintain a healthy physique, and understanding the science behind how our bodies uniquely handle food and exercise is a great first step in planning for a healthier future.
Sex Chromosomes: metabolic differences start at sexual differentiation
The significant sexual divergence in body composition between males and females begins at puberty [1]. Those who have inherited two “x” chromosomes (biologically female) begin to store more body fat than males (those with one “x” and one “y” chromosome). Statistically, after puberty, young women carry an average of 6% more body fat than males of the same age, this percentage difference grows each decade until post-menopause, when the 12% difference then begins to slowly decrease [1]. This phenomenon is observable, to some degree, in most mammalian species and is not specific to humans [1].
When a person becomes pregnant, they begin to store even greater proportions of fat that cannot be solely attributed to “eating-for-two” (or the added caloric intake during gestation) [1]. This means energy in versus energy stored is very different between men and women.
The reason for these sex differences in energy metabolism has yet to be determined definitively, but most hypotheses are related to sex steroids (estrogen and testosterone), differences in insulin resistance, or metabolic effects of other hormones such as leptin (the appetite regulator).
Why do men need more calories in a day?
The male metabolism has adapted for size, strength, and speed. On average, they have more lean muscle mass and tend to burn through visceral fat reserves more quickly, making more energy available for activity, and saving less in reserve for periods of fasting [2].
The more muscle mass a person has (regardless of sex), the more energy they will burn, as each muscle cell is using energy to function. As men are likely to have more muscle, they are likely to also use and burn more energy. Another part of these tendencies is based on the sex hormone, testosterone, which alone can boost metabolic rate [2].
Why do women have more fat stored?
Female bodies are genetically predisposed to store energy for functions that male bodies cannot perform, such as pregnancy and breastfeeding. The female metabolism has adapted to convert less dietary intake into muscle and bone, and burn less fat at baseline, storing energy for periods of fasting, to protect the potential nutritional needs of a fetus or infant [3].
Technically, this means women’s bodies run more efficiently than men’s, using less and storing more energy. Unfortunately, in times of plenty, this means we must be more careful to not overeat, as storage of too much fat can have serious consequences to our health.
In addition, there may be a role between sex and leptin signaling. Leptin is a hormone secreted by fat cells that should give us a feeling of satiation, curb appetite, and regulate the storage of new fat. Estrogens may interact with this signaling cascade to reduce our sensitivity to leptin signaling, causing more fat from the diet to be stored, compared to males [1].
There have also been links made between estrogens and water retention, uncomfortable bloating, and food cravings [3]. All of these are typical factors in the derailment of a healthy diet and exercise regimen.
Age: sex differences change over time
Although female bodies are likely to store more fat, they also have a lower incidence of obesity-related health problems and cardiovascular disease during childbearing years [4]. Menopause marks a significant increase in obesity-related health issues for females and a risk of cardiovascular disease that is equal to males’ [4].
Age takes a toll on male metabolism too. As testosterone levels naturally decline, so does their metabolic rate, giving further evidence that testosterone is a natural metabolism booster [5].
Generally, male bodies have more lean muscle mass, but everybody (male and female) tends to lose muscle mass as they age. This fact, along with a decrease in sex hormones, is likely responsible for the increased difficulty older adults often struggle with maintaining a healthy weight.
So What Can We Do?
Exercise
Unlike hormones, muscle mass can naturally be restored with strength training at any age. Remember that more muscle cells mean more energy used, both from the diet and from stored fat. This doesn’t mean we all need to be powerlifters. If lifting weights doesn’t suit you, consider bodyweight resistance training like yoga or pilates to build new muscle.
During exercise, women tend to use a higher proportion of stored fat as fuel than men, whose bodies prioritize glucose. However, post-workout, female bodies revert back to storage mode more quickly than males in response to circulating estrogen [1]. This may be evidence of the increased importance for women to balance muscle-building activities with endurance exercises like hiking, biking, and swimming for fat burning and weight management. More muscle mass will increase your metabolic rate, but women need to stay in exercise mode longer to free stored fat for use as an energy source.
Nutrition
What should we be eating and supplementing to help even the playing field?
Consuming a protein-rich diet is a great way to boost your metabolism. Foods like meat, fish, eggs, dairy, legumes, nuts and seeds, can all help to increase your metabolism for a few hours, by requiring more energy for your body to digest, absorb, and process the nutrients. High protein foods increase your metabolic rate by 15–30%, compared to 5–10% for carbs and 0–3% for fats [6]. When dieting for weight loss, protein-rich diets can also help your body hold on to its muscle mass, while losing fat [7]. Protein also helps to keep you feeling satiated for longer, fighting off hunger, which can prevent overeating [8].
If you’re eating a plant-based diet or finding yourself struggling to get enough protein, try adding Metabolic Maintenance’s amino acids to your diet. Even if you aren’t primarily plant-based, BAM Amino Acids will promote long-lasting energy for your workouts, and all of the important building blocks for new muscle protein thereby supporting a faster metabolism. There are some amino acids you can take individually that have functions relating specifically to fat mobilization. For example, L-Carnitine helps to transport long-chain fatty acids across the mitochondrial membrane for fat breakdown and energy generation. Because of its role in energy generation, not only is L-Carnitine a great supplement to aid in weight management for men and women, it also supports recovery after exercise and cardiovascular health [9].
One organ with a major influence over your metabolism is the thyroid gland. Iron, zinc, and selenium are three minerals necessary in a minimum abundance for the thyroid gland to perform its functions and produce metabolism-regulating thyroid hormones [10]. If you are not already, check your multivitamin/mineral formula to make sure it contains these nutrients. Many of Metabolic Maintenance’s multi formulas do contain these minerals.
Do you like spicy foods? Capsaicin, a chemical found in chili peppers, has been shown to help burn more calories through the day, control appetite, and has been linked to fewer calories consumed during a meal [11].
Water! Water may seem odd to add to this list, as it contains no nutrition, but it does play a key role in both digestion and muscular function [12]. Drinking water can act as an appetite suppressant; as the walls of your stomach expand from your drink, it stimulates the release of satiation hormones. Drinking water during exercise has been shown to increase the caloric expenditure of a workout and is a necessary component in the process of breaking down stored fat [12].
So, stay hydrated and don’t give up hope. Although there are some major differences in the way men and women consume, store, and burn the energy in the foods we eat, we all have the tools (and now the information) on how we can treat our bodies, at any age, to keep our metabolisms strong and our weight in a healthy range.
References
- Wu, Betty N., and Anthony J. O’Sullivan. “Sex differences in energy metabolism need to be considered with lifestyle modifications in humans.” Journal of nutrition and metabolism 2011 (2011).
- Dellitt, Julia. “How Is Metabolism Different in Men and Women?” Aaptiv Magazine. Accessed May 20, 2019. https://aaptiv.com/magazine/male-metabolism-common-questions
- O’Sullivan, Anthony J. “Does oestrogen allow women to store fat more efficiently? A biological advantage for fertility and gestation.” obesity reviews 10.2 (2009): 168-177.
- Shi, Haifei, Lynda M. Brown, and Roshanak Rahimian. “Sex/gender differences in metabolism and behavior: influence of sex chromosomes and hormones.” International journal of endocrinology 2015 (2015).
- Dellitt, Julia. “5 Things You Need to Know About Fat Loss for Women.” Aaptiv Magazine. Accessed May 20, 2019. https://aaptiv.com/magazine/fat-loss-for-women
- Pesta, Dominik H., and Varman T. Samuel. “A high-protein diet for reducing body fat: mechanisms and possible caveats.” Nutrition & metabolism 11.1 (2014): 53.
- Wycherley, Thomas P., et al. “Effects of energy-restricted high-protein, low-fat compared with standard-protein, low-fat diets: a meta-analysis of randomized controlled trials.” The American journal of clinical nutrition 96.6 (2012): 1281-1298.
- Lejeune, Manuela PGM, et al. “Ghrelin and glucagon-like peptide 1 concentrations, 24-h satiety, and energy and substrate metabolism during a high-protein diet and measured in a respiration chamber.” The American journal of clinical nutrition 83.1 (2006): 89-94.
- Wutzke, Klaus D., and Henrik Lorenz. “The effect of l-carnitine on fat oxidation, protein turnover, and body composition in slightly overweight subjects.” Metabolism-Clinical and Experimental 53.8 (2004): 1002-1006.
- Mullur, Rashmi, Yan-Yun Liu, and Gregory A. Brent. “Thyroid hormone regulation of metabolism.” Physiological reviews 94.2 (2014): 355-382.
- Ludy, Mary-Jon, George E. Moore, and Richard D. Mattes. “The effects of capsaicin and capsiate on energy balance: critical review and meta-analyses of studies in humans.” Chemical senses 37.2 (2011): 103-121.
- Huizen, Jennifer, “Can water help you lose weight?” Medical News Today. June 28, 2018. https://www.medicalnewstoday.com/articles/322296.php