Working out provides a host of body benefits: cardiovascular fitness, muscle tone, and—luckily for the well-conditioned—wiggle room for a sweet tooth.
“For a fit body, a candy bar will be pretty uneventful. Bits of sugar and fat will be processed, broken down, and shuttled off to cells. No biggie. The person will go and eat a nutritious dinner and move on,” says Ryan Andrews, R.D., a fitness, and nutrition coach.
The problem, then, isn’t one sweet, but the snowball effect of handful after handful. “It’s hard to give an exact number and say, ‘once you’ve hit this threshold, you’re officially overdoing it,’” says Andrews. But in general, he estimates 50 grams of sugar and 50 grams of fat in one concentrated, candy-filled dose is too much, even for an athletic body. (Two classic candy bars like Butterfingers or Milky Ways would put you over that sugar figure and almost halfway there in fat.)
“When we over-consume food beyond our needs, some negative things can start to happen,” Andrews says. “When that food is highly processed, like Halloween candy, it might be even more problematic.” Below, nutrition experts explain the physiological fallout of going hog-wild.
Your Brain: When sugar hits your tongue, the brain sends a message to the pancreas to produce insulin, a hormone that signals cells to either absorb sugar as energy (or glucose) in the muscles or store it in the liver, says Kristin Kirkpatrick, R.D., manager of nutrition services at Cleveland Clinic Wellness Institute. Your brain then activates its reward system and levels of dopamine increase, which may be what’s telling you to eat more of the sweet stuff, she says.
This can lead to skewed perceptions of reward and hunger in the brain, says Andrews. (Even if you’re full, you might keep eating.) “Over time, it can create a reward cycle and reliance on sugar to improve mood.”
Your Bloodstream: Excess fat, sugar, and sodium from sweets can increase blood volume, making your blood more concentrated, says Andrews. “This means higher blood pressure, which is bad news for vessels, kidneys, eyes, and the heart.” It might also limit how much urine you produce—which means you’ll hold onto extra fluids, he says.
Ultimately, the flood of fats and sugar must go somewhere, says Andrews. “Once cells have what they need, sugars can be converted to fats, and incoming fat can be stored away—as fat.”
Over time, if there’s constantly too much glucose circulating (from a high-sugar diet), cells’ sensitivity to insulin can weaken or they can stop responding all together. That can morph into type 2 diabetes, Kirkpatrick says.
Your Heart: If you’re eating dark chocolate—which has caffeine—you may experience an energy burst and your heart may start to beat faster, says Kirkpatrick.
Ingredients matter, too. For example, Andrews adds: Dark chocolate with coconut offers decent nutrients (like fiber, iron, magnesium), contains less sugar, and has good-for-you monounsaturated fats. A Kit-Kat is low-quality chocolate, dairy, and sugar. “The fats in coconut and dark chocolate are less likely to promote heart disease and more likely to be processed by the liver for energy,” says Andrews.
Your Immune System: After such a high dose, your immune function will likely be compromised, making you more susceptible to an illness, says Andrews. (When the bacterial balance in your gut is out of whack—see above—your entire immune system can be dialed up or down.)