The Truth About Weight Loss: Does a Prone-to-Weight-Gain Constitution Exist? An Analysis of Genetic Influence

Prone-to-weight-gain constitution:
Is there such a thing as a constitution where even drinking water makes you gain weight?

There are always those among us who seem to put on weight simply by drinking water, while others are the exact opposite—they eat no less than anyone else, yet remain slim no matter how much they consume.

So what exactly is going on here? Is there truly such a thing as a constitution that makes one prone to weight gain or weight loss?
In reality, a person's tendency towards obesity is significantly influenced by both innate genetics and acquired dietary and exercise habits.

Let us first address innate genetics. Some individuals are naturally predisposed to a more weight-gain-prone constitution, while others are inherently inclined towards a leaner build – this is indeed linked to genetic factors. Research indicates that approximately 40% to 60% of obesity in adults is associated with genetics.

So how exactly do obesity genes regulate weight?
Simply put, proteins encoded by obesity genes regulate appetite and energy expenditure, indirectly or directly leading to increased body fat. For instance, extensive research in mice has identified obesity-related genes that modulate appetite; disrupting these genes causes mice to become obese.
The genetic mechanisms of obesity are highly complex, often involving the interaction of numerous genes. The metabolic effects of consuming the same amount of food vary between individuals, affecting digestion, absorption, and energy conversion. Similarly, energy expenditure during identical exercise levels differs among people, and efficiency in utilising food may also vary – all factors with significant genetic components.

Certain obesity genes, for instance, can significantly increase appetite, leading to higher energy intake. Individuals with variations in the FTO gene (FTO stands for Fat Mass and Obesity) may exhibit a stronger preference for high-fat, fried foods, and sweets, consuming an average of 100 kilocalories more per meal. Research also indicates that some individuals possess fewer dopamine receptor genes, meaning they require larger food portions to achieve sufficient pleasure.

Furthermore, gene expression is influenced by environmental factors, which can modulate gene activity. The rising prevalence of childhood obesity stems from the affordability and accessibility of junk food, which tempts many FTO gene variant carriers. Excessive stress can also activate obesity genes, significantly increasing appetite. When individuals face pressures such as financial difficulties, work stress, or exam pressure, it ignites a craving for high-sugar, high-fat foods. Consuming these foods reduces the body's stress hormones.

Beyond genetics, parental dietary habits are also passed down. Children of non-obese parents tend to adopt healthier, more restrained eating patterns, consuming fewer calories. If both parents enjoy exercise, their offspring may develop a natural affinity for physical activity from an early age. This leads to higher muscle mass, a faster basal metabolic rate, and greater energy expenditure.
Additionally, innate digestive capabilities vary significantly. Some individuals remain slim regardless of intake, potentially due to weaker gastrointestinal systems where digestion and absorption processes malfunction. Food is expelled before proper digestion occurs, naturally preventing weight gain. If you fall into this category, refrain from complacency – such constitutions are inherently weaker, with compromised immunity, constituting a state of suboptimal health.

Moreover, intestinal length and the composition of gut microbiota influence nutrient absorption, contributing to variations in body shape.

All these factors fall under the category of innate influences on obesity. At this point, observant readers might question: Wasn't the sole condition for weight gain previously stated as energy intake exceeding expenditure? How does this relate to genetics? In truth, these concepts are not contradictory. For instance, individuals with obesity-prone genes may be more inclined to consume high-calorie foods or expend less energy, leading to surplus calories being stored as fat. In other words, those with obesity-related genes may find it harder to create an energy deficit for weight loss, requiring greater effort than others. Genetics reflects the relative ease or difficulty of gaining weight, but it does not mean individuals with such genes will inevitably become obese without cause. The fundamental principle that weight is determined by energy imbalance remains constant.