No long can you lie about your diets or indulge in extra cheat days without getting caught, thanks to a new blood test assessment. Researchers from the University of Eastern Finland set out to prove it’s possible to determine if someone is following their diet and published their findings in the Journal of Nutrition.

The new Nordic SYSDIET study reveals how a simple blood test can be used to track the compliance of dieters and find out if their diets are giving them the benefits they seek. Researchers analyzed 154 participants’ cardiometabolic risk factors, including elevated blood pressure and blood lip levels, in order to determine if their diet was being followed correctly and they weren’t lying about their nutritional intake. The study’s lead author Dr. Matti Marklund and his colleagues used dietary biomarkers related to certain foods that could measure bodily tissues and fluids, such as their blood levels. One group was required to follow the Nordic diet rich in berries, vegetables, fatty fish, canola oil, and whole grains, similar to a Mediterranean diet.

The test will reveal if participants swayed from their diets, which oftentimes happens when you completely cut out a food group or don’t give yourself cheat days once a week. High-fat diets with dairy intake were easily revealed in the blood tests and researchers were able to assess the entire diet and its success as a whole. In order to avoid relapsing, it’s easier for people to change their behavior by taking each day at a time and not completely locking a food group, such as carbohydrates, away or else they’re more likely to give in to temptation.

In future studies, researchers will combined biomarker checkups with participants’ diet journals in order to evaluate how the impact of their diet functions throughout their body and can be used as a motivate to limit fatty foods from their diets by seeing the test results. The typical diets Americans try every year consist of putting limitations on added sugar, refined grains, sodium, and saturated fats, according to the President’s Council on Fitness, Sports & Nutrition. With 78 million U.S. adults and 12.5 million children clinically obese, the test could serve as a monitor for people and their doctors to help them lower their bad food intake.

Source: Riserus U, Thorsdottir I, Marklund M, Magnusdottir OK, Rosqvist L, Cloetens R, et al. A Dietary Biomarker Approach Captures Compliance and Cardiometabolic Effects of a Healthy Nordic Diet in Individuals with Metabolic Syndrome. Journal of Nutrition. 2014.