Do you try to watch what you eat and exercise regularly, only to find yourself staying the same weight - or even piling on the pounds?
Meanwhile your best friend stuffs herself with pizza and drinks like a sailor, but stays as slim as ever.
It's frustrating, but it could be down to you having a slower metabolism - meaning you burn calories for energy at a reduced rate.
Everyone's metabolism is different and based on a number of factors including height, weight, genetics and activity levels.
Understanding how your metabolism works could be the key to losing weight - and tests exist to help you figure it out.
What is metabolic testing?
Metabolic testing tells you how many calories you're burning while at rest (aka, your resting metabolic rate or RMR).
Your RMR will tell you what your daily calorie needs are, which can help you come up with a diet plan tailored to your weight loss goals.
There are different types of metabolic testing, including direct calorimetry (measuring your body heat to determine the number of calories you burn), indirect calorimetry (measuring how much oxygen you consume compared to the amount of carbon dioxide you breathe out) and VO2 max text (measuring your body's ability to consume oxygen).
Direct calorimetry is very expensive and rarely takes place outside of a research or lab setting, while VO2 tests or usually for athletes.
Indirect calorimetry is the most affordable and accessible option.
Where can you get tested?
Metabolic testing used to only be available at hospitals and weight loss clinics, but now many gyms, sports medicine facilities and dietitians offer the service.
Some people feel the testing done in gyms is less accurate than those carried out by medical professionals, so don't be afraid to ask questions about the equipment used.
What else do I need to know?
According to Women's Health, you shouldn't eat or have any caffeine, alcohol or nicotine in the hours before your test.
You should also avoid exercising beforehand as it will affect the accuracy of the results.
After the test, you can work with a personal trainer or dietitian to come up with a weight loss plan that's designed specifically for you.