Unraveling the Complex Web of Eating: From Glucose Theory to Environments

As Summer creeps upon us closer and closer, it might be advantageous to review some theories of eating that will help us keep in shape all year long!
Eating is a behavior as natural as breathing, yet its underlying mechanisms are anything but simple. In this article, we'll take a deep dive into the myriad theories that attempt to explain why we eat what we do, when we do. We’ll look at the abatement of these theories and we’ll propose why managing your weight can be so difficult and why there is a deeper influence happening when we eat.
So, we’ll discuss some theories of eating and how, over time, even the best explanation can end up being a shortfall.

Glucose Theory: The Paradoxical Problem
Our exploration begins with the Glucose Theory, which posits that our body's glucose levels directly influence our eating behavior. When glucose levels drop, the parasympathetic nervous system is primed, and beta cells in the pancreas release insulin, signaling the body to eat. Likewise, when glucose levels rise after eating, it signals fullness and satiety. This theory, however, isn't without its contradictions. For instance, the body's use of glucose presents a paradox; although it is a primary source of energy, the body's reactions to its consumption and regulation can appear counterintuitive, complicating our understanding of hunger and satiety signals.
Central Control Theory and the VMH & LH Debate
Moving deeper into the brain, in studying the Central Theory of Eating, specifically how the Ventromedial Hypothalamus (VMH) and Lateral Hypothalamus (LH) control eating behavior, lies in their seemingly opposite roles that are yet interdependent. Historically, the VMH has been labeled as the "satiety center," meaning its activation is thought to cause cessation of hunger and lead to feelings of fullness. Conversely, the LH has been considered the "hunger center," with its activation promoting eating and hunger sensations.
The contradiction emerges when these areas do not act as simple on/off switches for eating behavior but rather as parts of a complex system that regulates energy balance, responding to various signals, including hormonal and neural. The paradox is that while these centers can stimulate or inhibit eating under certain conditions, their interactions, and the influences of external factors like stress, availability of food, and palatability make the regulation of eating behavior far more complicated than a straightforward binary system.
Additionally, newer research has shown that this dichotomy is overly simplistic. Neurons in both the VMH and LH can either promote or inhibit feeding depending on their type and the signals they receive, which further complicates the traditional view of VMH and LH roles in eating behavior.
Gordon Kennedy, a British physiologist, made significant contributions to our understanding of brain feeding centers and body weight. His elegant studies challenged the prevailing belief that hypothalamic “centers” directly control eating behavior. Kennedy’s work demonstrated that these centers do not have a direct role in regulating food intake. He came to this conclusion after examining mice who had their VHM damaged and reached obesity but did not explode rather they stopped gaining weight. Further, he found that if you exposed these same mice to caloric restriction they did, in fact, lose body weight and fat, however once they returned to their previously normal eating routine, they became obese, again. This led to our current understanding of “Set Point” theory which, essentially, it suggests that despite fluctuations due to diet or lifestyle changes, the body will eventually return to its "set point" weight range. This theory implies that long-term weight change is challenging to achieve outside of one's biological set point range without considerable effort or changes to one's physiological makeup.
So, if the “set point” theory is true, what is regulating our body weight and fat stores? How is it doing that and what is it measuring to be able to do that?
Leptin: The Hormone That Changed Everything
The mid-1990s brought a significant breakthrough with the discovery of Leptin, a hormone produced by fat cells. Leptin and its receptors in the hypothalamus were seen as the keys to unlocking the mysteries of appetite control and obesity. Initially, it appeared that leptin could perfectly support the set point theory, in fact, all the puzzle pieces of this unknown mechanism of control fell into place in the immediate years. Additional studies indeed, found that there were leptin receptors in the hypothalamus which confirmed the idea that the hypothalamus could be regulating the amount of leptin in our bodies.
However, the perfect explanation into weight control was dashed just a few years later. A pivotal 1996 study revealed that obese individuals often had high levels of leptin, naturally present in their bodies, which was contradictory to set point theory. Further, clinical tests were completed by injecting obese individuals with high levels of concentrated leptin, yet the additional leptin supplementation did not affect their body fat levels. This finding suggested that leptin resistance, rather than deficiency, might be a critical factor in obesity, challenging the notion of a simple solution to weight regulation.
Abating Biological Theories of Eating

As you can see, each of the discussed theories provides valuable insights but also faces significant challenges when confronted with empirical evidence. The biological regulation of body weight, influenced by practices such as fasting, skipping meals, and overeating, continues to be a complex field of study. These factors underscore the importance of considering multiple angles and contributors to eating behavior and weight regulation.
A concept to underscore is that there is no single neuro-chemical specificity or complex neural chemistry to control eating behavior. The complexity of the organs discussed, and others, is not focused on a single biological state of homeostasis.
Environmental Determinants: The Power of Context

Perhaps one of the most tangible influences on our eating behavior is our environment. Factors like portion size, the variety of available foods, and the presentation of meals significantly impact our consumption habits. Did you know that mixed foods, like casseroles and stir fry dishes, result in less food being consumed versus if they were served in their compartmentalized forms.
Also present are the social, interpersonal, and stress related influences on our eating behavior. With those accounted for, our evolved and sharply honed instincts toward nourishment and food sources make us opportunistic eaters. This recognition shifts the spotlight to the psychological aspects of eating, acknowledging that our environment can trigger eating behaviors independent of physiological hunger cues.
The variety and abundance of food in our surroundings can stimulate overeating, while large portion sizes may distort our perception of what constitutes a 'normal' meal. This environmental influence extends beyond mere temptation, highlighting the complex interplay between psychological triggers and physiological needs. We must be aware that we do not simply consume information about food; that information is a trigger in our eating behaviors.
Conclusions on Psychological Influence and Food Priming
What can we conclude? Well, it's crucial to acknowledge that eating is not solely governed by internal physiological cues but is also heavily influenced by external environmental factors.
The concept of Food Priming suggests that our evolutionary history of opportunistic eating behavior may still influence us, driving us to eat whenever the opportunity arises, regardless of hunger.

Consider a concept that suggests rather than having a fixed "set point" for body weight, our bodies operate within a flexible weight range. Within this range, managing homeostasis—controlling blood sugar, fat stores, energy expenditure, and metabolic rates—is more straightforward. Essentially, it's a zone where our body's regulatory systems function optimally and minimally. Outside this range is a set of lifestyle behaviors that one may not be incorporating into their lifestyle.
This is intriguing because it suggests adaptability and the real possibility of influencing our health outcomes through lifestyle choices. Here are some examples to illustrate this idea:
1. Physical Activity and Exercise: Regular exercise is a key factor in maintaining a healthy weight and metabolic rate. Activities such as brisk walking, cycling, or swimming can help keep the body within its comfortable operational range by burning excess calories, improving cardiovascular health, and enhancing muscle mass, which in turn can increase metabolic rate. Engaging in physical activity regularly can also help prevent the body's regulatory systems from needing to "reset" to a new, less healthy range due to sedentary behavior1.

2. Nutrition and Diet Choices: Consuming a balanced diet rich in fruits, vegetables, whole grains, and lean proteins can support the body's homeostasis by providing essential nutrients without excessive calories. Avoiding processed foods high in sugar and saturated fats is crucial, as these can disrupt blood sugar levels and fat stores, pushing the body outside of its optimal range. A well-balanced diet helps maintain energy balance and supports metabolic functions at their best2.
3. Stress Management: Chronic stress can have a significant impact on the body's regulatory systems, including blood sugar levels and fat storage. Techniques such as deep breathing, meditation, yoga, and spending time on hobbies or with loved ones can mitigate stress's effects on the body. Managing stress effectively helps prevent the body's operational systems from shifting into a less healthy state, maintaining the body's homeostasis within its adaptable range3.
4. Adequate Sleep: Consistent, high-quality sleep is essential for maintaining the body's homeostasis. Lack of sleep can affect hormonal balance, appetite regulation, and energy expenditure, leading to weight gain and metabolic disturbances. Ensuring a regular sleep schedule and creating a conducive sleeping environment can support the body's regulatory systems in staying within their comfortable range1.
5. Hydration: Proper hydration is crucial for maintaining metabolic rate and energy expenditure. Water plays a key role in numerous bodily functions, including digestion and temperature regulation. Staying well-hydrated helps ensure that the body's operational systems work efficiently and remain within their adaptable range.
These examples underscore the importance of lifestyle behaviors in influencing the body's regulatory systems and maintaining homeostasis within a correctable range. Adopting healthy habits can help prevent the need for the body's systems to "reset" to a new operational state that may be less conducive to overall health and well-being123.
This intricate dance between our bodies, our brains, and our environment underscores why managing eating behaviors and body weight is so challenging. It also emphasizes the need for a multifaceted approach that considers the psychological, physiological, and environmental determinants of eating. By understanding these diverse factors, we can better navigate the complex world of eating behavior and work towards healthier lifestyles. The goal of the article was to raise some awareness about how we all can react to information about food: the commercial food advertisers know about it: I just thought you should too!