Why Do My Breath Test Results Rise Later in the Day?

If you’ve just started your breath testing journey with FoodMarble and you’ve noticed that your results often trend upwards as the day goes on, you’re not alone. This is a common pattern, and there are two important factors that can help explain why:

1. Gastric Transit Time

Gastric transit time is the amount of time it takes for food and drink to move through your digestive system. This varies widely between people, but here are some general timelines:

• Food can reach the small intestine within 1–2 hours.
• Food usually reaches the colon within 3–8 hours.

Because of these timings, the food you ate for lunch may not affect your fermentation levels until later in the afternoon or evening. Similarly, your dinner may continue influencing your digestion well into the night.

Transit time is influenced by many factors, including:

• The types of foods eaten (e.g., fatty meals tend to slow digestion, while high-fiber or liquid meals move faster).
• Stress levels and emotional state.
• Sleep quality and timing.
• Exercise habits.
• Medications or supplements.

👉 This is why it’s helpful to log not just meals, but also lifestyle factors in your FoodMarble app. Over time, you’ll start to see how these elements interact with your digestion.

2. FODMAP Stacking

Even when following a low FODMAP diet, portion size and food combinations matter. FODMAPs are cumulative—meaning they can stack up in your system across meals.

• A single FODMAP-containing food (e.g., a small portion of apple at breakfast) may be well tolerated on its own.
• But if you eat other FODMAP-containing foods later in the day (e.g., bread at lunch and onions at dinner), the combined load may push you past your threshold, leading to increased fermentation and symptoms.

This explains why it’s not always your most recent meal that’s causing your levels to rise. Sometimes it’s the stacking effect across multiple meals and snacks throughout the day.

Putting It Together

If you’ve noticed that your results are usually lower earlier in the day but rise in the evening or nighttime, two things may be at play:

1. Gastric transit time — food eaten hours earlier is only now reaching the colon, where fermentation peaks.
2. FODMAP stacking — foods that seemed fine in isolation may combine to tip you over your threshold later in the day.

Key Tips to Keep in Mind

• Track consistently: Log meals, snacks, lifestyle habits, and symptoms in the app.
• Look at the bigger picture: Don’t assume the last meal was the “trigger.” Consider food combinations and timing.
• Experiment with portions: Reducing quantity, spacing out meals, or adjusting ingredients may help lower fermentation scores.
• Be patient: Patterns often become clearer after a few weeks of consistent testing and logging.

✨ By considering both gastric transit time and FODMAP stacking, you’ll gain a clearer understanding of your digestion and make more informed decisions about what works best for your gut.

Updated on: 17/08/2025