Why Do Fat Burners Make Me Feel Nauseous?

Fat burners are often marketed as a secret weapon for weight management, but they can sometimes make you feel nauseous, among other potential side effects. The reasons for this can lie in the ingredients and because of the way they affect the digestive process.

Types of Fat Burners

Fat burner supplements or medications are designed to promote fat loss by increasing metabolism (the rate at which your body uses food for energy), suppressing appetite, or helping the body break down stored fat more efficiently. 

Fat burners fall into two categories:

• Stimulant-based — These options often include caffeine or other compounds that stimulate the central nervous system. Common in over-the-counter supplements, stimulant-based fat burners work to boost thermogenesis—your body’s heat production process that’s tied to calorie burning.
• Non-stimulant-based— These fat burners focus more on appetite regulation and metabolic adjustments without relying on stimulants. Many require a prescription and work by influencing hunger hormones and blood sugar levels.

Common Ingredients & Their Effects

Many fat burners are packed with powerful and concentrated ingredients designed to curb hunger and speed up your metabolism. Understanding these ingredients and how they work can help you see why they can upset your stomach. 

Nausea linked to fat burners often occurs due to rapid metabolic shifts which disrupt digestion, hormonal changes from suppression of hunger hormones, or overstimulation of the nervous system, which you’ll see explained more for each ingredient below. 

Caffeine

• How it works — Caffeine stimulates the central nervous system to break down fats and release energy your body can use. The heat generated in both the stomach and colon can lead to discomfort.
• Side effects—Nervousness, jitteriness, nausea, vomiting, and in extreme cases, even tachycardia (rapid heart rate).
• Good to know — Though coffee has caffeine in it, your daily coffee won’t burn significant fat, especially if paired with creamers or syrups, which add excess calories.

Green tea extract

• How it works — Caffeine and a compound known as EGCG in green tea team up to enhance fat and calorie burning. This can contribute to discomfort in the stomach and colon as well.
• Side effects — Concentrated caffeine can contribute to nausea, especially in higher doses, along with jitteriness and in some cases, a rapid heart rate.
• Good to know — Drinking multiple cups of green tea throughout the day would be required to match the effects of a small supplement dose.

Capsaicin

• How it works — Capsaicin, the compound that gives chili peppers their heat, works by temporarily increasing feelings of fullness and encouraging fat burning. It can also help burn calories.
• Side effects — Overconsumption can cause gastrointestinal distress, nausea, bloating, and increased insulin levels.
• Good to know — Fat-burning benefits from capsaicin are short-lived and may not support long-term weight loss.

GLP-1 receptor agonists

• How they work — GLP-1 receptor agonists, now commonly known for their role in prescription weight loss medications, suppress the hunger hormone, ghrelin, which helps to slow digestion and regulate blood sugar levels.
• Side effects — Nausea is one of the most common side effects, especially as your body adjusts to the way the medicine affects digestion. Other side effects include constipation, diarrhea, dizziness and headaches. (See Common Side Effects of GLP-1 Weight Loss Medicationsfor more info.)
• Good to know — GLP-1 medications for weight loss are intended more for people seeking long-term weight management rather than quick weight loss to reach a goal for a specific event. The good news is the nausea and other digestive side effects lessen as you get used to the drug.

Tips to Minimize Nausea

If you experience nausea from taking fat burners, the following actions might help:

• Lower the dosage — Always consult your doctor or other healthcare professional, especially with side effects of prescription medications.
• Stay hydrated — Drink water throughout the day to support digestion.
• Eat small, frequent meals — Try taking the fat burner with food to help limit nausea.
• Consider ginger — Some people find nausea relief from consuming ginger in the form of drinks, supplements, chews, and other forms.

If you’re considering taking fat burners, be sure to discuss them with your doctor first to be safe. While they can temporarily boost metabolism and aid in weight loss, they are not a tool for sustainable weight management. And in addition to nausea and other side effects listed here, you may not be able to take them if you have certain health conditions or are on certain prescription medications.