If you think adding coconut oil and butter to your morning coffee, instead of the more unusual cream or milk, is good for your health, you are mistaken according to dietary experts.

“Bulletproof Coffee” or “Butter Coffee” quickly became a trend after tech entrepreneur Dave Asprey founded Bulletproof Nutrition Inc in 2014 and opened its first bulletproof coffee store in Santa Monica in 2015.

The bulletproof coffee became an instant hit among people who followed the keto diet. The brew that blended coffee with butter and medium chain triglyceride oils (MCTs) or coconut oil soon became a favored replacement for breakfast for people who were in the state of ketosis. At present, there are also websites like KetoConnect offering people recipes to make the perfect bulletproof coffee.

And when is the right time to drink this kind of coffee? "Bulletproof coffee is designed to be drunk on an empty stomach instead of breakfast and prior to working out as it helps to increase energy and endurance. This is due to the combination of caffeine and fats fuelling the body. It is very high in calories and fat which is why it is recommended that it replaces a meal and not drunk with a meal, which would lead to consumption of excess calories and potential weight gain,” nutritionist Fiona Tuck told the Huffington Post Australia.

Supporters of this coffee blend claim that it improves energy, boosts metabolism and also helps one lose weight. However, a number of the dietitians have raised concern on the assumed benefits of bulletproof coffee.

In an article about caffeine trend in lifestyle magazine, My Body And Soul, Melissa Meier, a Sydney-based Accredited Practicing Dietitian, analyzed the nutritional value of the ingredients added in bulletproof coffee and found that it harms one’s health more than actually improving it.

“Butter (a key ingredient in BPC) is a rich source of unhealthy saturated fat that can increase your risk of heart disease,” she wrote.

She also questioned the use of coconut oil in the coffee mix. “While the specific type of saturated fat in coconut oil acts differently in some ways to others (it can raise ‘good’ HDL cholesterol) – at the end of the day, it also raises ‘bad’ LDL cholesterol, which isn’t good news for your ticker,” she opined.

MCTs, on the other hand, she agreed were more useful than butter or other edible oils since they were water soluble and tends to go straight to the liver rather than stay in the bloodstream. However, Meier seemed doubtful that it aided in weight loss in any way, like bulletproof coffee drinkers might be claiming.

“I think it’s more of a money-making gimmick. Adding butter by the tablespoon to your morning coffee is simply unnecessary – so carry on as you would and please don’t ruin your perfectly delicious brew,” she added.

Meier’s opinion was echoed by Katherine Zeratsky, a Mayo Clinic dietitian, who said that most people don’t realize the long term health hazard caused by drinking this specific coffee blend.

“Coffee can be a very rich source of antioxidant in many people’s diets,” Zeratsky said, South Florida Reporter reported. “When you add things like butter and coconut oil to your coffee, you’re adding a significant amount of saturated fat and a significant amount of calories. We worry, that those extra calories and the imbalance it might be creating in your diet might not work for you and your long-term health.”

Instead, she advised people to pair up their morning Cup of Joe with some fruit and a bit of protein for a wholesome and healthy breakfast.