Unused calories get stored as fat, which is a great mechanism.

But our goal is to not let these stores overfill.

When they get overfilled, it might take a bit more effort to keep these stores at low levels because proteins produced by fat can suppress heat production. This helps explain why individuals with more fat often find it harder to lose weight (Whittle et al., 2015; Rosen & Spiegelman, 2014).

The body also tries to maintain a baseline level of fat for optimal function, and this baseline can rise when you consistently consume excess calories. Therefore, the goal is to not over-overfill these stores too much by using the calories in workouts (Friedman, 2014; Speakman & Levitsky, 2005).

The brain needs calories too, so office work uses up calories, and calories are essential for a productive life.

The body needs calories too when doing a workout, and also calories to repair.

Today, we live more sedentary lives doing more brain work, but our bodies have evolved for active lifestyles, so it’s important to consciously work out to keep our bodies healthy and functioning.

This birthed the gym — a man-made place to mimic the life our bodies have evolved to function in: lifting and carrying heavy objects.

One way to check the rate at which our bodies have stored unused calories is enter your body fat percentage and compare yourself to the general population to get a percentile rank.

https://athleticpursuit.io/body-composition-rank

10% rank means 90% of people in your demographic have lower body fat % than yourself.

90% rank means you have lower body fat % than 90% of people in your demographic.

You can’t conclude that being in the 90% rank means that’s the optimal rank for you, but you can conclude that about 43% of adults worldwide are overweight (BMI ≥25), meaning nearly half the global adult population carries excess fat stores, and 16% are classified as obese — far above what is considered healthy. A healthy range is between 10–15% for men and 18–25% for women. (World Health Organization, 2025).

References

Whittle, A.J., Jiang, M., et al. (2015). sLR11/SorLA represses thermogenesis in adipose tissue and correlates with BMI in humans. Nature Communications. https://www.cam.ac.uk/research/news/stored-fat-fights-against-the-bodys-attempts-to-lose-weight

Rosen, E.D., & Spiegelman, B.M. (2014). What we talk about when we talk about fat. Cell, 156(1–2), 20–44. https://doi.org/10.1016/j.cell.2013.12.002

Friedman, J.M. (2014). Leptin and the endocrine control of energy balance. Nature Metabolism. https://doi.org/10.1038/nm.2827

Speakman, J.R., & Levitsky, D.A. (2005). Energy balance and body weight regulation. American Journal of Clinical Nutrition, 82(1), 289S–296S. https://doi.org/10.1093/ajcn/82.1.289S

World Health Organization. (2025). Obesity and overweight fact sheet. World Health Organization. https://www.who.int/news-room/fact-sheets/detail/obesity-and-overweight