Should We Stop Eating When We Feel “Full”? – Dr. Ralph Carson

Many well-meaning people attempt to stop eating when they are “full.” And most of us assume that this ability — to notice if we feel hungry or full — will come to us easily and naturally.
 
We may believe that if we pay attention to our own hunger and fullness, we will naturally consume the appropriate amount of food — giving us the right amount of energy and helping us maintain our “natural weight.”
 
If we don’t pay attention to our hunger and fullness cues, though, we might eat too much, leading to weight gain or obesity. This leads to a few important questions:
 

• Does every person know how to recognize physical sensations of hunger and fullness?
• Are stomach cues really enough to rely on, in order to know when to eat and when to stop eating?
• And after years of sporadic dieting, can one lose touch with these signals? If so, how does one know if they are experiencing true hunger?

We are designed to eat for pleasure

Many adults and even children will tell you that they understand what hunger and fullness feel like. They may say, “hunger is when my stomach feels empty and has little pangs in it.” “Fullness is a feeling of discomfort, pressure or tension in my stomach.”
 
Research shows that, regardless of how “full” we may feel, our bodies are still hard wired to seek reward — leading some people to habitually overeat. In order to help our species survive, eating for pleasure (taste, smell, mouth feeling and appearance) will almost always override eating to the point of satiation (fullness). As a result, we are often tempted to overeat when we are presented with our favorite or highly palatable foods.
 
And here is the reason why: for decades, our bodies became accustomed to eating whole foods from natural sources rather than the highly processed foods available today. In our modern society, thanks to plentiful cheap food, this balance has been disrupted for many individuals. As a result, the brain is confused and inappropriate fullness feedback occurs. This can result in binge eating and excess fat storage (36) (Bauer ’15).

Frequently asked questions about hunger and fullness

With so many people struggling with overeating, can science and medicine help bring balance back to our hunger and fullness systems? I address some common questions about hunger and fullness below:

1. Does binge eating or restricting affect feelings of hunger and fullness? —When people alternate between binge eating and restricting, the body struggles to recognize how much food intake will be necessary before fullness will be achieved. This phenomenon is likely irreversible and an individual who habitually does these behaviors will no longer have the capability to tune into fullness.
2. Does weight affect stomach capacity? — We are hard-wired to have a certain gastric capacity. Studies of gastric emptying in normal-weight and obese persons have shown inconsistent results (14) (Park ’05). You might assume that people of normal weight typically have lower gastric capacity than people of higher weights. But research has shown that normal weight binge eaters have an even larger gastric capacity than the obese (16, 18) (Geliebter ‘01b, ’04). One theory as to why this occurs is this: as weight (degree of obesity) increases, the likelihood of binge eating also increases. This explains why the gastric capacity of morbidly obese individuals is so large (19) (Yanovski ’93). 
3. Can gastric stimulation help us feel full? — A gastric electric stimulator (GES) manipulates gastric signals and produces a sense of fullness (1, 2) (Chu ’12; Mizrahi ’12). Here’s how it works: eating food trips a sensor that sends a signal to the device. Electrical activity within the stomach muscles sends continuous waves from the entry and eventually the outlet of the stomach. The gastric stimulator quickly tricks your brain to register fullness by stimulating these stomach muscles. The theory behind this is that the GES should increase feelings of fullness, reduce food intake, prevent overeating and contribute to weight loss. But does it work? Several assessments have concluded that there is insufficient scientific evidence to support gastric stimulation (3, 4, 5) (SBU ’04; Buchwald ’02; Salvi ‘09). Such exploration does provide insight that suggests reliance on gastric stimulation as an accurate indicator of fullness is unreliable. Consequently, a gastric stimulator is not recommended.
4. Can vagal nerve blockage reduce hunger? — The vagal nerve plays a significant role modulating sensations of feeling hungry. Cutting the vagal nerve decreases appetite and reduces weight, but there is little evidence suggesting it plays a significant role in long-term weight maintenance (10) (Berthoud ’08). VBLOC ® vagal blocking therapy is designed to intermittently block the vagus input from the stomach to part of the brain linked to hunger (11) (Mamitt ’15). Periodically, the device delivers an electronic impulse that blocks hunger impulses, potentially leaving the patient feeling fuller, reducing food intake and lowering body weight. But, the device does not address behavioral and lifestyle changes: healthy eating habits, making healthy choices, addressing emotional eating or promoting physical activity. Thus, experts recommend prioritizing diet and exercise over vagal blocking devices to maintain one’s weight (13) (Dixon ’11).

Eating to survive vs. eating for pleasure

In summary, we know that the body is constantly working to control food intake by balancing the need to survive (homeostatic) with a desire for pleasure (hedonic).
 
At times, defective brain signaling occurs. This will shift the balance between the survival and pleasure systems — causing pleasure to take over. This may explain why humans overeat on a highly palatable diet even when they are full. And it also addresses why, over time, this ultimately impairs the ability to control caloric intake, leading to long-term weight gain.
 
The emphasis on when to stop eating should be based on “satisfaction” which is achieved through mindful eating. Relying on stomach fullness cues will not only be inaccurate but frustrating for those who are either hard-wired to have increased gastric capacity or have altered their feedback signaling through disordered eating. 

About the Author:
 
Ralph Carson, RD, PhD, is a nutritionist and exercise physiologist with over 40 years of experience. He is currently Vice President of Science and Innovation for Eating Recovery Centers (ERC). Dr. Carson is an active member on the board of the International Association of Eating Disorder Professionals (iaedp) and author of The Brain Fix: What’s the Matter with Your Gray Matter.
 
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