Why Weight Loss In Adults Can Be Tough After Childhood Overfeeding

Weight loss in adults can be daunting. Despite following a strict diet and exercise regimen, the dream of maintaining those ‘decent figures’ may seem distant for many adults. The question: Why is weight loss tough for many adults?

Medical (e.g., hormones), lifestyle (e.g., sleep deprivation), environmental (e.g., stress), and biological (e.g., genetics) factors challenge weight maintenance.¹ Among these, an often-normalised practice, childhood overfeeding, can alter the expression of your genes, leading to persistent obesity.²

This article explores the challenges adults overfed as infants face in healthy weight management. It addresses how overfeeding infants can contribute to the development of childhood and adult obesity.

Why you should care

Obesity is now recognised as a global health crisis. For context, between 2022 and 2023, 26.2% of adults (18 years and older) in England were obese, and 64.0% were overweight or with obesity (Office for Health Improvement & Disparities, UK). 

A sedentary lifestyle, consumption of unhealthy and high-calorie food, disturbed sleep cycle, underlying medical conditions, or certain medications can add unwanted body fat.¹

This unwanted weight gain can shape one into being overweight or obese, with health implications.³

Weight loss strategy to manage obesity: Does it always work?

Weight gain that leads an individual to be overweight or obese is due to the accumulation of excess fat in the body, stored within packets or cells called adipose cells.³

The location of these packets with excess fat in the body can pose a danger to the functioning of the organs. Thus increasing future health risks, including chronic diseases.⁴

Preclinical obesity is a condition in which excess accumulated fat in the body is present. The individual has normally functioning organs; however, they are at a high risk of developing chronic diseases like type 2 diabetes.⁴

Preclinical obesity should be mitigated by eliminating the main culprit, the extra fat. Behavioural, diet, and lifestyle modifications, in addition to medical interventions, can manage preclinical obesity.

Losing the gained weight by 5 to 10% and managing it is reported to significantly improve an individual's health and quality of life.^3,4 But is weight loss or its maintenance that easy?

Learn more about obesity, its diagnosis, and ways to manage it.

Why weight loss and maintenance can be challenging

Weight loss from dietary measures and exercise can efficiently manage preclinical obesity and reduce the need for medical treatments (medications or surgery).⁴ However, many find it difficult to lose weight or maintain the lost weight.^1,5

Figure 1. Factors that challenge weight loss or management. By Smruthi G Prabhu

Figure 1 summarises the factors that make weight loss in adults and its maintenance a challenge. Biological factors pose a challenge in weight management. 

Genetics determines who you are and what you look like. However, did you know you can still have control over your genes? Your lifestyle, nutrition choices, and environment influence which genes are turned on or off, i.e., altered gene expression.⁶

Simply put, our DNA functions like an instruction manual, with genes as the words that guide how our body operates.

However, environmental factors—like highlights or strikethroughs—can influence how these words (genes) are read. This changes the instructions our body follows and alters gene expression.

To summarise, gene expression is partly controlled by the environment. For the weight parameter, 50% is determined by our genetic makeup and 50% by the environment. ⁵

So, the next time you cut back on sleep, remember—it can alter the expression of genes for hormones that increase hunger and lead to overeating.¹

Altered gene expression: Is it reversible?

Altered gene expressions that lead to weight gain, healthy or unhealthy, can be reversed with weight loss interventions.⁶

Most often, weight loss in adults can be achieved by addressing the factors that led to extra fat accumulation with exercise, caloric restriction, a diet plan, and positive lifestyle and behavioural changes.⁶

However, this may not always be applicable, especially if the changes in gene expression (changed instructions) occur in the earliest stages or years of life.⁷

Childhood overfeeding: Does it program the body for obesity?

Sociocultural factors, parental unawareness, and availability of high-calorie food (e.g., baby formula) are the causes of childhood overfeeding.

Overfeeding translates to a calorie surplus and overnutrition. With studies reporting feeding habits of infants in the early days to determine their future health, weight, and obesity risk, what is optimal feeding?^8,9

The risk of overfeeding in a baby who is breastfed is low. Breastmilk hormones help regulate the feeling of fullness and hunger, thus avoiding overfeeding an infant.¹⁰

However, the risk of overfeeding is high when circumstances demand baby formula and bottle feeding. Though formula companies recommend 60-90 ml of formula every 3 hours in a newborn (day 1), research suggests that newborn infants receive no more than 30 ml per feed.⁸

To ensure your child receives proper nutrition, ask your paediatrician for instructions on age-appropriate volumes to feed or food to avoid overfeeding and promote responsive feeding.

How does a baby’s nutritional environment contribute to obesity

From a child’s conception till it reaches 2 years of age, its genetics are open to changes by interacting with various environmental factors.⁹ Hence, the birth parents’ health during pregnancy, diet while pregnant and breastfeeding, and the infant’s nutrition decide the child’s wellness.⁸

Improper feeding practices in infants less than 2 years of age cause rapid weight gain.⁸ Obese infants are at higher risk of staying so well into adolescence and adulthood. Owing to the altered gene expressions from gene-nutrition interaction, these changes program obesity in infants:

• Excessive appetite

The development of the hypothalamus, a part of the brain that regulates hunger and energy expenditure, can be affected by excess nutrition during the third trimester or overfeeding thereafter.²

The hindered development of the appetite-regulating region of the brain causes permanent appetite changes, including its control, leading to increased food intake and weight gain as the child grows.²

• Increased fat reserves

Adipose tissues store fat as energy reserves for the smooth functioning of the body. When in need, these stored fats fuel the body.

Overfeeding with proteins through high-calorie formula increases these energy reserves (white adipose tissue) in the infant.^8,10 However, the surplus energy reserves (adiposity) established during childhood are irreversible.¹¹

Nevertheless, are these energy reserves (adipose tissues) accessible?

• Changes in metabolism

Nutritional factors can turn genes that instruct and control enzyme production on or off.¹⁰

A turned-on gene (ACAC-B) boosts the production of an enzyme that blocks access to the energy reserves (stored fats) to fuel the body. Thus, promoting more food intake for energy leads to more fat storage. 

With fat metabolism blocked, the stored fat remains unused.

It is now established that changes in metabolism formed during infancy persist into adulthood.⁸

• Changes in hormone balance

Feeding of formula or overfeeding in early infants, early feeding of solid food, and obesity in the birth parents during pregnancy result in higher blood glucose and serum insulin levels.^8,9,10,12

Excess nutrition in early life stages changes the expression of genes involved in insulin sensitivity of the cells. The resulting insulin resistance leads to higher blood glucose and instructs more insulin production by the body.¹²

High serum insulin levels have critical effects on brain (hypothalamus) development and adiposity. ^8,10

The adipose tissues secrete leptins that regulate appetite in association with the hypothalamus. Abundant adipose tissues mean accelerated leptin secretion. Yet there is persistent hunger as the hypothalamus does not respond to the leptins.

Insulin resistance, an underdeveloped hypothalamus, adiposity, leptin resistance, and changed metabolism create a vicious cycle contributing to weight gain and obesity. 

Therefore, adults overfed as infants are programmed to gain weight and, hence, struggle to lose or maintain weight loss without medical treatment.

FAQs

Is it true that adipose tissues remember obesity?

Yes, adipose tissues remember the instructions or programming effects of external factors (nutrition) on genes to store extra fat.¹³

Adults programmed to be obese in infancy struggle to manage weight because the fat cells remember and resist weight loss.¹³ Additionally, the brain, with a similar memory, yearns for food.¹⁴

As the years of obesity determine the tissue's memory, prolonged duration of the prescribed diet could erase the memory of obesity.¹⁴ Hence, it is important to stick to the prescribed diet even after weight loss surgeries or medical treatments. 

Summary

• Accumulation of excess fat because of one’s lifestyle, nutritional choices, and environment causes weight gain
• Medical, lifestyle, environmental, and biological factors challenge weight management
• Environmental factors partly control gene expression, influencing mechanisms that promote weight gain or loss
• Exercise, caloric restriction, a diet plan, and positive lifestyle and behavioural changes can reverse the altered gene expressions, making weight loss possible
• A child’s genetics are open to changes from their conception to 2 years of age by interacting with various environmental factors, including nutrition
• Gene-nutrition interactions can change gene expressions in infants, leading to excessive appetite, increased adipose tissues, and metabolic and hormone level changes that will resist weight loss even in adulthood