How Does Spiciness Affect Food Intake?

This Week’s Research Highlight

How much we eat feels like a personal choice. An internal calculation driven by our energy needs.

But in reality, that decision is shaped by factors we scarcely notice.

The size of the plate. The weight of the portion. Whether the food is cut into pieces. Subtle cues like these can influence intake in measurable ways, even when hunger and taste stay the same.

For instance, in one study, participants who served themselves lunch on 9-inch plates wound up eating 23% more than those using smaller plates.

It’s not just the food itself. It’s how we perceive it and interact with it.

And that interaction goes beyond visual cues. Sensory elements, like texture and temperature, can alter how much we eat.

One such variable has received little attention, despite being one of the most potent stimuli we ever encounter at the table, is spice.

Capsaicin, the compound that gives chili peppers their heat, is known to trigger pain receptors and elevate heart rate. Some research suggests it might suppress appetite or increase energy expenditure. But in practice, spice can also intensify flavor, stimulate cravings, and keep us reaching for more.

So which is it? Does spice blunt intake by disrupting appetite, or amplify it by enhancing reward?

A team of researchers at Penn State decided to find out.

Designing a Controlled Dose of Burn

To test how spice influences eating behavior, researchers at Penn State ran a series of three controlled lunch experiments. They recruited healthy adults from central Pennsylvania, excluding both spice fiends and spice haters to keep tolerance from skewing the results.

The protocol was the same across all three: participants came to the lab twice, once for a mild version of the test meal, and once for a spicier version, created by adjusting the ratio of sweet to hot paprika.

Everything else stayed constant: same portion size (650 grams), same recipe, same presentation. The experiments varied only in the dish or the spice intensity:

• Experiment 1: Beef chili — a familiar, hearty dish
• Experiment 2a: Chicken tikka masala with a moderate paprika blend
• Experiment 2b: The same tikka masala, but with a higher dose of hot paprika

Before and after each meal, participants rated their hunger, fullness, and how spicy they found the food. They also sampled a bite to rate how much they liked it, helping researchers distinguish changes in intake from changes in enjoyment.

Spicier Meals, Smaller Portions

Turning up the heat led people to eat less — a modest but meaningful drop.

In Experiment 1, participants were served a beef chili that came in two versions: one mildly spiced, one made entirely with hot paprika. The spicy version led to a 13% reduction in intake, or about 46 grams less food eaten on average.

Turning up the heat reduced intake. In Experiment 1, participants ate 46 grams less when served a spicy version of the beef chili.

Experiment 2b tested the same idea using chicken tikka masala. When the spice level was high enough to be clearly felt, participants ate 18% less than they did with the mild version. Different meal, same outcome.

But the effect wasn’t automatic. In Experiment 2a, the team used a lower dose of hot paprika — enough to change the recipe, but not enough for participants to reliably detect a difference in spice. In that version, there was no difference in intake.

That failure turned out to be useful. It suggested the effect only appears when the heat is noticeable — a threshold response, basically.

Replicating the effect in a different meal. In Experiment 2b, participants ate 64 grams less, an 18% reduction, when the chicken tikka masala was made with a spicier paprika blend. The effect held even with a different dish, cuisine, and protein source.

The difference in intake was clear, but not easily explained. People weren’t less hungry, didn’t like the food any less, and didn’t drink more water. They just stopped eating sooner.

That’s when the researchers turned to the video footage.

The Hidden Variable: Eating Speed

The researchers weren’t just tracking how much food people ate. They were watching how they ate it.

Each meal was recorded in high definition and analyzed frame by frame. Trained coders logged every bite, every sip, every pause. In the process, they turned lunch into data, and chewing into a key behavioral variable.

And that’s where it got interesting.

In both successful trials — the chili and the higher-spice chicken tikka — participants ate more slowly when the food was spicy. In the chili trial, eating rate dropped by 11%, driven by fewer bites per minute. In the tikka trial, it dropped by 17%. People didn’t stretch out the meal, or take smaller bites. They just paced themselves differently.

And that, it turns out, was enough to make all the difference.

Once eating speed was factored in, the effect of spice on intake disappeared. Spice didn’t change how much people wanted to eat; it changed how fast they got there.

Spice slows eating in chili. Spicier chili led to an 11% drop in eating rate, driven by fewer bites per minute. Bite size and meal duration stayed the same.

Replication in tikka masala. Spicier chicken tikka caused a 17% decrease in eating rate. The pattern matched what was seen in the chili trial.

Why Eating Speed Matters

What determines how much we eat isn’t just what’s on the plate. It’s how quickly it disappears.

Faster eating is consistently associated with higher energy intake, both at individual meals and across the day. The underlying reason seems straightforward: the body needs time to register fullness, and when we eat quickly, those signals can lag behind consumption.

This is where oral processing comes into play: the set of behaviors that includes chewing, bite pacing, and how long food stays in the mouth. Anything that slows these processes down tends to reduce overall intake. And that effect appears to hold even when the food itself doesn’t change.

Take food texture, for example. In one classic experiment from the 1970s, researchers served participants the same amount of apple in three different forms: whole pieces, applesauce, and juice. Eating time varied dramatically — 17 minutes for whole apples, 6 minutes for applesauce, and just 90 seconds for juice — and so did satiety. The faster the food went down, the less satisfying it seemed.

From Haber et al, 1977.

More recent research confirms this pattern. Harder foods, which require more chewing, reliably slow down eating and reduce intake, even when calories and nutrients are held constant.

That’s likely one reason ultra-processed foods promote overeating: they’re engineered to be soft, easy to chew, and swallowed quickly. In a tightly controlled metabolic ward study at the NIH, participants ate over 500 extra calories per day on an ultra-processed diet compared to a minimally processed one, despite the meals being matched for calories, macros, fiber, and palatability.

When researchers looked closer, they found that participants ate the ultra-processed meals much faster — and that eating speed largely explained the difference in calorie intake.

All of this points to a simple principle: slowing down how we eat — by any means — can reduce how much we eat.

From Hall et al, 2019

How Much Spice is Enough?

The key takeaway from this study is that adding spice to a meal can reduce how much people eat — but only if the burn is strong enough to be noticeably felt. When the added spice was too subtle, the effect was abolished. When it was clearly perceptible, but not overwhelming, people ate 13–18% less.

That reduction worked out to about 50-70 fewer calories per meal. A small calorie cut, but one that could definitely add up over time if it were sustained.

So how much spice are we actually talking about here?

Well, in the two successful experiments, meals contained between 12 and 26 grams of hot paprika per 650 gram portion, or 1.8% to 4% of the total meal weight.

For a typical 400 gram home-cooked dish, that would translate to roughly 7 to 16 grams of hot paprika, or 1.5 to 3 teaspoons (depending on grind and variety).

That’s more than what you'd find in a mildly spiced recipe, but not so much that it ruins the meal for someone with a moderate spice tolerance.

If you're already used to some spice, nudging it up a notch may be all it takes to naturally slow your eating pace. And if you're more spice-sensitive, even a tiny increase may do the trick.

Summary: In a series of controlled lab experiments, researchers at Penn State tested whether adding spice to familiar meals would influence how much people ate. Across two trials — one using beef chili, the other chicken tikka masala — participants ate 13–18% less when the meal was made spicier, but only when the heat was strong enough to be clearly perceived. Appetite ratings and food liking remained unchanged, suggesting the effect wasn’t driven by hunger or aversion. Instead, video analysis revealed that participants ate more slowly. Eating rate dropped by 11% in the chili trial and 17% in the spicier tikka trial, and this shift in tempo fully explained the reduction in intake.

Random Trivia & Weird News

🦷 An early twentieth-century health guru insisted that we should chew every bite at least 32 times.

In the early 1900s, wellness crusader Horace Fletcher built a movement around one rule: chew your food until it’s liquid. He claimed this practice could improve digestion, reduce food waste, and cure just about anything.

Dubbed “The Great Masticator,” Fletcher even convinced luminaries of the era like John D. Rockefeller and Henry James to join the slow-chewing revolution, which became known as Fletcherism.

His ideas were kind of…extreme (he reportedly chewed soup), but oddly prescient in light of recent research into the impact of oral processing. Fletcher may have taken it too far, but he wasn’t entirely wrong.

Horace Fletcher: "Nature will castigate those who don't masticate."

Podcasts We Loved This Week

• Sharon Horesh Bergquist: Longevity through stress — unlocking your body’s survival pathways. Via The Proof.

• Charles C. Mann: How Norman Borlaug stopped the apocalypse. Via Plain English with Derek Thompson.

Products We Like

Wildbrine Korean Style Kimchi

If you’re looking to experiment with foods that naturally slow your eating pace, kimchi is a great place to start. It delivers the burn — but also crunch, chew, and complexity. The texture forces you to slow down, and the spice adds just enough heat to break the autopilot rhythm of fast eating.

This particular variety is easy to find at Whole Foods and other major grocery stores. It’s bold enough to make an impact, but not so fiery it hijacks your meal, so it is likely to hit that “just right” zone for most people.

humanOS Catalog Feature of the Week

The Simple Food Diet

Developed by neuroscientist Stephan Guyenet, the Simple Food Diet is designed to lower calorie intake without counting, restriction, or battles with willpower.

It works by targeting the brain systems that regulate appetite, using food structure, cooking methods, and meal design to subtly reshape how you eat. As a result, you eat less because you’re satisfied — not because you’re forcing it.

To Access:

1. Log in to humanOS.
2. See Programs in navigation on the left-hand side
3. Click Ideal Weight Program.
4. Scroll down to Simple Food Diet (near the bottom, on the right).

Wishing you the best,