Several years ago, I was sitting in a graduate school conference, listening to a nutrition expert speak about how addictive food can be. She brought up the now infamous “sugar vs. cocaine rat” study, as well as how certain foods are broken down into opioid-like substances in our brains. For example, dairy becomes casomorphin and gluten is broken down into several morphine-like substances called gluten exorphins (also known as gluteomorphins or gliadorphins).

At the time, I thought, “Wow! I guess there’s a real, biological explanation as to why comfort foods, like mac and cheese, are comforting!” It also helped explain some aspects of binge eating disorder and why some people have difficulty with feeling out of control around food. It all made sense to me, and I left the conference feeling ready to present this new information to my clients who felt like they were addicted to food.

One question haunted me, however: How do people who are supposedly addicted to food avoid the very thing we all need to live?

What seemed so clear-cut and absolute at the conference suddenly felt very confusing.

“Our bodies cannot be addicted to things that they need for survival, which is what food and sugar are,” explains Ashley Wentworth, MS, RD, CD, owner of Ashley Wentworth Nutrition. “They are necessary components for life. Sugar and carbohydrate foods are our main energy sources. The body is constantly seeking these foods for nourishment and fuel.”

When asked about studies that suggest sugar can be addictive, Wentworth responded, “Research supporting food or sugar addiction likely has not controlled for food restriction, dieting history, weight cycling, eating disorders and disordered eating behaviors, and stress levels. Stress, especially chronic stress, has a physiologic response that takes a lot of energy for the body to produce, including releasing glucose into the bloodstream. This response requires more energy from the body, in turn requiring more fuel.”

She also pointed out that many of the studies that investigated the addictiveness of sugar have used rats that had not been fed or had been fed intermittently. If they’re hungry, of course they’re going to seek out food.

“A review by Westwater et al. reported that they could find little evidence to support sugar addiction in humans, and that the addiction-like behaviors found in animal studies occurred more likely because of interrupted access to sweet-tasting or highly palatable foods, and not because of the neurochemical effects of sugar,” explains Ronette Lategan-Potgieter, PhD, a visiting assistant professor in nutrition and health sciences at Stetson University.

In an article for The Guardian, one of the researchers for this review, Hisham Ziauddeen, pointed out that in studies like the classic “Intense Sweetness Surpasses Cocaine Reward” study, researchers got the same kind of effects whether they used sugar or saccharin (a calorie-free artificial sweetener), and “so it seems to be about the sweet taste, rather than sugar.”

And yet other studies suggest signs of sugar addiction. “Other researchers, however, support the notion of sugar addiction and report that an addiction to sugar seems dependent on the natural opioids the body releases after sugar consumption,” comments Lategan-Potgieter.

One such study proposed that “there is strong evidence for sugar addiction, and that their model demonstrated five out of 11 criteria for substance use disorder (SUD). “From an evolutionary perspective,” the study authors state, “we must consider addiction as a normal trait that permitted humans to survive primitive conditions when food was scarce.”

But is this really addiction? Or is it a normal biological reaction our bodies have to restriction of food, including starvation?  

Restriction…or Addiction?

There is research that shows that when food is restricted, such as with dieting, the brain goes into survival mode, putting thoughts of food at the forefront and into hyperdrive. One key study in this area is the Minnesota Starvation Study in which researchers recruited 36 young, healthy men and restricted their calories to approximately 1370 kcal/day (note that this isn’t even as low as the 1200 kcal/day often recommended by weight-loss experts).

Besides losing, on average, 25% of their body weight, these young men became totally preoccupied with food. They talked about it, read cookbooks and collected recipes. They had difficulty focusing and were easily distracted. They became very possessive with their food while eating and even paranoid that others might try to take their food. Some started excessively chewing gum, to the point where researchers had to place a limit on packages of gum chewed a day to two per person; still others developed a habit of smoking tobacco to help ease the hunger pains. Some were observed rummaging through garbage to find food, while others started cutting their food into tiny pieces to extend the length of mealtime. Even participants who had described themselves as being more extroverted prior to the study began to isolate themselves. Other symptoms participants developed included anxiety, depression, gastrointestinal issues, dizziness, hair loss, headaches, edema, cold intolerance and a 40% decrease in their basal metabolic rate (BMR).

These aren’t isolated findings. A review of the literature on starvation and self-imposed dieting shows similar findings to the landmark Minnesota Starvation Study.

So, what does this all mean in relation to sugar addiction?

“Restriction of food, including sweet foods, can be a large cause of the feelings of addiction,” says Wentworth. “Once food is restricted, our brains sense this restriction and cause increased thoughts of food, as well as increased hunger signals, which help us find food. Our bodies do not know the difference between purposeful restriction, as with dieting, versus lack of access to food.”

In other words, if studies are using rats that have not been fed enough, it’s natural that they’ll seek out the food option—or what they perceive as food, as in the case of the saccharin.

It’s also a natural, biological process that occurs when humans cut calories or food groups. If you’re not eating enough, whether it be calories or nutrients, your brain will become like a cranky toddler, constantly at you until you give in and give it what it wants. Or as in the case of this study using actual toddlers, when we’re deprived of tasty, palatable foods, it’s exactly what we end up craving and wanting.

“In our society, we are constantly told and sent the message that we can’t trust our bodies to nourish us,” comments Wentworth, “and that we have to find nutrition plans or programs to follow. This leads to restriction and sets us up for feeling out of control around food, especially sweet foods. Studies have shown that restriction leads to binge eating and obsessive thoughts about food. Using an ‘all foods fit’ intuitive eating approach to food and nutrition can lessen the burden of restriction and reduce the cravings and binging that come with it.”

Sugar May Not Be Essential, But Glucose Is

While sugar has been villainized—including natural sugars found in fruit and dairy—it’s important to remember that glucose is necessary for our bodies to function properly.

“Every cell [in our bodies] relies on glucose for energy and glucose is the preferred energy source for the brain, nerve cells and developing red blood cells,” explains Lategan-Potgieter. “Without maintaining normal blood glucose levels, the human body cannot function optimally, and without an adequate supply of glucose available, athletes do not perform well.”

The Pleasure Center

So far, we’ve seen how our food intake is driven by our nutrient needs and food deprivation. “But as Freeman et al. explains, our food choices and intakes are also influenced by reward neurotransmitters, like dopamine and serotonin, as well as opioids and cannabinoids naturally produced within the body,” explains Lategan-Potgieter. “Consumption of palatable foods, usually high in fat and sugar, releases dopamine, which encourage continued intake. Freeman et al. also concluded that there are two main aspects linked to reward with sugar intake, namely the taste and the nutritive effect.”

“Certain foods, like sugar, can activate the reward system in the brain,” agrees Maddison Saalinger, MS, RDN, LDN, a nutrition educator for the Diabetes Research Institute. “The reward system can activate the ‘pleasure center’ that reinforces the body to seek that experience or food again and again. This repetitive food-seeking behavior is what some may call ‘food addiction.’”

Wentworth adds, “People who consume high amounts of sugar also start exhibiting a ‘tolerance’ to it, which means they need to consume more to receive the same dopamine response. This makes it more difficult to avoid sweet foods.”

Some other factors that can also influence the reward system, adds Saalinger, include one’s environment, as “some people are exposed to these foods more than others.” For example, heading to the vending machine every afternoon at work for a candy bar is a daily habit that can be challenging to break. Additionally, some people learn to respond to uncomfortable emotions and stress by consuming certain foods.

Saalinger adds that high-sugar, high-fat foods are highly marketed, easily accessible and low cost. “These foods usually do not contain nutrients that are satisfying, and therefore, people may feel they need a greater amount to reach that ‘fullness.’”

Clearly, numerous factors influence food choice. And despite some alarming headlines over the last few years, research has not definitively proven sugar addiction, as there are many credible studies that refute it. Perhaps the truth lies somewhere in the middle. As a health and exercise professional, it’s important to consider the literature on both sides and be cautious when making absolute claims one way or the other.