Do Birthdays Determine Leanness?

Author: Dani Shugart

Introduction

The question of whether one's birthday can influence body fatness is a curious one. New research posits an affirmative answer, while common sense would seem to suggest otherwise. This article delves into a rather unconventional study exploring this topic.

The Conceptual Link: Conception and Metabolism

Consider the moment of your conception and the ambient temperature at that time. This might seem an odd connection, but it could potentially be an indicator of your metabolism. If your birthday falls within the autumn months (September, October, November), you were likely conceived during colder months. Research from Japan indicates that if a mother conceives during these cold periods, the offspring is more likely to possess a higher quantity of brown adipose tissue (BAT), which in turn facilitates easier maintenance of a lean physique.

Understanding Brown Adipose Tissue (BAT)

It's crucial to note that having more BAT is beneficial. Brown fat is metabolically more active compared to white fat. Thus, a higher BAT content makes it simpler to remain lean. While the "constitutive" BAT present at birth diminishes with age, it doesn't completely disappear. Interestingly, there are strategies to transform a portion of adult white fat into "inducible beige fat," which we will explore later. First, let's examine how those conceived in winter (and born in autumn) may have a metabolic edge.

The Study

Methodology

Researchers conducted an analysis on 356 young males. Employing imaging techniques, they measured the participants' brown adipose tissue and evaluated aspects of their overall metabolic health, including visceral fat accumulation, body mass index (BMI), and daily energy expenditure. Additionally, they gathered the participants' birth dates to estimate the time of conception. Weather data was then utilized to determine the outdoor temperatures during these estimated conception times.

Findings

The study revealed that individuals conceived during colder months demonstrated more BAT activity, increased energy expenditure, lower BMI, and reduced visceral fat in adulthood. These results imply that the temperature at the time of conception may program BAT activity and impact metabolic health in later life.

Lifestyle Trumps BAT

Debunking the Birth Month - Leanness Link

Just because you weren't born in the "right" month doesn't mean you're destined for a particular body composition. Lifestyle choices play a far more significant role. When we consider whether autumn - born babies typically grow into lean adults or if those born in other months are more prone to overweight, no clear trends emerge. If there was a distinct pattern where fall - birthday individuals were consistently lean and others overweight, it would be noticeable, and astrologers might even claim some cosmic connection between Libras and leanness (a rather absurd notion). While the study suggests that the development of BAT due to the season of conception may offer some advantage for leanness later on, common sense dictates that behavior is of greater importance.

Examples of Non - Autumn - Born Lean Individuals

For those still concerned about the implications of this study, consider a list of well - known bodybuilders who have achieved remarkable leanness despite not having autumn birthdays:

• Dorian Yates - April

• Shawn Ray - May

• Sergio Oliva Jr. - May

• Ronnie Coleman - May

• Arnold Schwarzenegger - July

• Kai Greene - July

• Frank Zane - June

These men may have had supplementary aids, but even without them, through diet and exercise, they would have been capable of achieving fitness, if not extreme muscular definition. Moreover, numerous natural lifters born outside the autumn season have become conspicuously lean, and many autumn - born individuals carry excess body fat. (The author, a September - born, attests to this.)

Increasing BAT in Adulthood

Activation and Browning of Fat

While activating the BAT you were born with is possible, developing new BAT as an adult is challenging. However, it is feasible to make white adipose tissue (WAT) browner. When white fat is "browned," scientists refer to it as beige or "brite" (a combination of brown and white). Turning white fat beige can increase energy expenditure throughout the day. Here are some strategies for browning white fat:

1. Cold Exposure

This includes activities such as ice baths, cold showers, cryotherapy, or brisk winter walks without a jacket. However, one must exercise caution to avoid endangering their life. Some fitness professionals caution against cold exposure, claiming it doesn't enhance muscle growth. This argument is as fallacious as saying "Don't wipe! It doesn't prevent colon cancer!" Cold exposure can be used as a strategy for goals other than building biceps. If cold exposure immediately after a workout may reduce its hypertrophy impact, it can be done prior to training, hours after a workout, or on an off - day.

2. Exercise

Exercise prompts the production of a hormone called irisin, which promotes the conversion of white fat into beige fat. High - intensity interval training (HIIT) and endurance training are particularly effective. For those who wish to avoid cold exposure, getting out of breath through exercise can be an alternative.

3. Get Enough Sleep

Maintaining sufficient sleep and a consistent circadian rhythm influences BAT activity. Even if it didn't, there are countless other reasons why the body and mind function better with adequate rest.

4. Diet and Supplementation

Certain compounds in foods and supplements can assist in developing browner, more metabolically active fat:

• Resveratrol: Research on humans, mice, and cell cultures indicates that resveratrol (available on Amazon) aids in converting white fat into brown. It activates the protein SIRT1, increasing brown fat and reducing white fat, thus promoting fat browning and energy expenditure.

• Cyanadin 3 - glucoside: C3G (available on Amazon) helps by increasing the mitochondrial content of white fat, transforming it into more metabolically active beige fat.

• Omega - 3 Fatty Acid: It activates brown fat cells by interacting with the GPR120 receptor, triggering the release of the hormone FGF21, which boosts energy burning. Similar to resveratrol, omega - 3s also increase the expression of genes like UCP1, enabling cells to burn fat for heat instead of storing it. Additionally, as chronic inflammation suppresses white fat browning, high - dose, inflammation - reducing fish oil (available on Amazon) should be consumed.

• Capsaicin: The spicy component in peppers increases thermogenesis and may activate BAT. For some, this can be as uncomfortable as an ice bath.

• Catechins: The compound in green tea can increase energy expenditure and assist in browning white fat.

References

• Yoneshiro, T., Matsushita, M., Fuse - Hamaoka, S. et al. Pre - fertilization - origin preservation of brown fat - mediated energy expenditure in humans. Nat Metab (2025).

• Andrade, João M. O., et al. "Resveratrol Increases Brown Adipose Tissue Thermogenesis Markers by Increasing SIRT1 and Energy Expenditure and Decreasing Fat Accumulation in Adipose Tissue of Mice Fed a Standard Diet." European Journal of Nutrition, vol. 53, no. 7, Oct. 2014, pp. 1503 - 1510, doi:10.1007/s00394 - 014 - 0655 - 6.

• Kim, Sangsu, et al. "Resveratrol Exerts Anti - Obesity Effects via Mechanisms Involving Down - Regulation of Adipogenic and Inflammatory Processes in Mice." Biochemical Pharmacology, vol. 81, no. 11, June 2011, pp. 1343 - 1351, doi:10.1016/j.bcp.2011.03.012.

• Vatner, Dorothy E., et al. "Brown Adipose Tissue Enhances Exercise Performance and Healthful Longevity." Aging, vol. 16, no. 1, 2024, doi:10.18632/aging.206179.

• Kim, Minji, et al. "Fish Oil Intake Induces UCP1 Upregulation in Brown and White Adipose Tissue via the Sympathetic Nervous System." Scientific Reports, vol. 5, 17 Dec. 2015, article 18013, doi:10.1038/srep18013.

• Kim, Jinkuk, et al. "EPA and DHA Differentially Modulate Adipose Tissue Formation and Beige Adipogenesis in Diet - Induced Obesity in Mice." The Journal of Nutritional Biochemistry, vol. 38, Dec. 2016, pp. 1 - 12, doi:10.1016/j.jnutbio.2016.08.009.

• Quesada - López, Tania, et al. "The Lipid Sensor GPR120 Promotes Brown Fat Activation and FGF21 Release from Adipocytes." Nature Communications, vol. 7, 18 Nov. 2016, article 13479, doi:10.1038/ncomms13479.