By Dr. Mercola
Ghrelin has been dubbed the "hunger hormone" because in previous studies people given the hormone became so ravenous, they ate markedly more than their usual food intake.
Ghrelin may act on your brain's "pleasure centers," driving you to reach for another slice of cheesecake simply because you remember how good the first one tasted and made you feel (at least in that moment).1 In short, one of the forces driving you to eat (and overeat a second helping or an extra dessert even though you're full) is, without a doubt, ghrelin.
What influences levels of this hormone in your body is another matter entirely -- a rather complex one at that. One of the most intriguing findings to date, however, is the power of your mind to fool your stomach in a sense, resulting in dramatic declines in ghrelin even in the absence of an indulgent meal.
The 'Mind Over Milkshake' Experiment: Your Mindset May Alter the Hunger Hormone
The video above gives an entertaining synopsis of psychologist Alia Crum's "milkshake experiment," which set out to determine whether the information on a food's nutrition label could prompt physical changes in your body.
For the study, participants were treated to a 380-calorie milkshake that was labeled in one of two very different ways. One label said the milkshake was a 620-calorie "indulgent" shake, the other, a 140-calorie "sensible" shake. It turns out that both the physical changes and the satiety levels in the participants matched what was written on the label, rather than what was actually in the cup.
Those who thought they were consuming the indulgent milkshake had a dramatically steeper decline in ghrelin after consuming the beverage, while those who thought they drank a sensible milkshake had a "flat" ghrelin response.
Meanwhile, the indulgent milkshake drinkers felt more satisfied, showing that "participants' satiety was consistent with what they believed they were consuming rather than the actual nutritional value of what they consumed."
So it turns out that your mindset may have a greater impact on your ghrelin levels than even the nutrients you consume, and this has major implications! By believing that the meal you've just eaten is satisfying, it may, in fact, drive down your hunger hormone, which has the secondary effect of revving up your metabolism to start burning the calories you've just eaten.
The researchers explained: "The effect of food consumption on ghrelin may be psychologically mediated, and mindset meaningfully affects physiological responses to food."
Why Diet Foods Don't Help You Lose Weight
The study sheds light on yet another reason why diet foods so often fail in helping people to actually lose weight. Remember, when people drank the sensible shake (which was advertised as having no fat, no added sugar, and being low-calorie), their ghrelin levels were relatively unchanged. This means their bodies were not getting the signal that they're full and should stop eating, nor were they getting an appropriate boost in metabolism.
As was expressed in the video, if food manufacturers really wanted to help people lose weight, perhaps labeling foods as full of fat and calories would do the trick better than advertising a diet product, which is unlikely to evoke a positive set of beliefs in most people.
Other studies have also shown that your brain is not fooled by foods that offer a sweet taste without accompanying calories, such as those that have been artificially sweetened. Experiments have found that sweet taste, regardless of its caloric content, enhances your appetite and induces an insulin-releasing effect.
In a nutshell, when you eat something sweet, your brain releases dopamine, which supplies you with a jolt of pleasure. Your brain's reward center is activated. The appetite-regulating hormone leptin is also released, which eventually informs your brain that you are "full" once a certain amount of calories has been ingested.
In contrast, when you consume something sweet but non-caloric (i.e. an artificial sweetener), your brain's pleasure pathway is still activated by the sweet taste, but there's nothing to deactivate it, since your body is still waiting for the calories. As a result, you may end up overeating and ultimately gaining weight.
What Else Influences Your Hunger Hormone?
It's becoming increasingly clear that what drives people to eat certain foods, and what triggers them to start or stop eating, is influenced by many factors. Your beliefs about a food may be one of them, but there are others, too. For instance, chronic lack of sleep increases ghrelin, making you feel hungry when you don't really need to eat. This is likely one reason why a lack of sleep can make you gain weight.
Insulin may also play a role in regulating ghrelin levels. In one study, ghrelin levels were monitored in eight non-diabetic adults as they were given a two-hour infusion of insulin. Shortly after the infusion began, levels of ghrelin began to drop. When the insulin infusion was stopped, levels of the hunger hormone began to rise and rapidly returned to normal.2
Since insulin is already known to increase levels of leptin -- the "obesity hormone" that tells your brain to curb your appetite after eating -- the findings suggest that insulin plays an important role in controlling what you eat.
In other words, let's say you eat a sugary dessert. Your production of insulin increases so that the sugar in your blood can be taken to cells and used for energy. Eating this sugar also increases production of leptin, which regulates your appetite and fat storage, and decreases production of ghrelin, which helps regulate your food intake. The idea is that when you eat, your body knows it should feel less hungry. However, when insulin is impaired (such as in cases of insulin resistance), ghrelin levels remain elevated even after meal consumption – a condition that leads to chronic hunger (mostly for carbs), excess food intake, and undesirable weight gain.
Fructose May Also Interfere with Proper Ghrelin Levels
Fructose, a cheap form of sugar used in thousands of food products and soft drinks, can damage human metabolism and is likely fueling the obesity crisis. This is because your body metabolizes fructose in a much different way from glucose, and fructose is now being consumed in enormous quantities, which has made the negative effects much more profound. If anyone tries to tell you "sugar is sugar," they are way behind the times. It is increasingly becoming clear that just by eating fructose, including high-fructose corn syrup, you may be drastically increasing your tendency to overeat. You see, glucose suppresses the hunger hormone ghrelin and stimulates leptin, which suppresses your appetite. Fructose, however, has no effect on ghrelin and interferes with your brain's communication with leptin, resulting in overeating.
This is why fructose may contribute to weight gain, increased belly fat, insulin resistance, and metabolic syndrome -- not to mention the long list of chronic diseases that are related to these conditions. It's also yet another example of the complex relationship your hunger hormones have on your ability to regulate your food intake. Still, the notion that your mind and your beliefs about what you're eating also influence your levels of ghrelin is fascinating and deserves due attention. As NPR reported:3
"'Our beliefs matter in virtually every domain, in everything we do,' Crum says. 'How much is a mystery, but I don't think we've given enough credit to the role of our beliefs in determining our physiology, our reality. We have this very simple metabolic science: calories in, calories out. People don't want to think that our beliefs have influence, too,' she says. 'But they do!'"
A Mind-Body Approach to Weight Loss Is Best
In a study of proven strategies that worked at helping people lose weight and keep it off for at least one year, many of the strategies were emotional in nature, including:4
- Avoid eating in response to negative emotions and stress
- Be accountable for your decisions
- Foster a sense of autonomy, internal motivation and self-efficacy toward weight loss maintenance
- Establish a social support network
There are often emotional factors underlying weight gain, so it's important to do some regular emotional housekeeping. Meditation, prayer, yoga, and energy psychology tools such as Emotional Freedom Technique (EFT) are all viable options that can help you relieve stress and clear out hidden emotional blocks that may be keeping you from achieving your weight loss goals (or sticking with a healthier diet).
The other element is that many people are still avoiding the very foods that will lead to those feelings of satiety that your mind is craving – foods like full-fat butter, coconut oil, nuts, avocados, and other health-boosting fats. Although there are clearly individual differences, most people would do well to strive for a diet high in healthful fats (as high as 50-70 percent of the calories consumed), moderate amounts of high-quality protein, and abundant vegetables. This type of diet will optimize your hormone levels (ghrelin, leptin, and insulin), ultimately leaving you feeling satisfied in mind and body, so you don't struggle with feelings of deprivation that may wreak havoc on your hunger hormone levels and metabolism.
In fact, research shows that calories gleaned from bread, refined sugars, and processed foods promote overeating, whereas calories from whole vegetables, protein, and fiber decrease hunger. Calories are simply not created equal, which is why trying to lose weight by counting calories doesn't work, but eating the right foods does. For a comprehensive nutrition guide for optimal health, weight, and satisfaction, refer to my comprehensive nutrition plan.