QUICK TAKE | Can Deepinder Goyal’s ₹85,000 Temple Wearable Really Track Blood Flow to the Brain? Seven Things to Know

1. What is Temple, and why is Deepinder Goyal in the news?

The Zomato co-founder is selling a small optical sensor that sticks to the side of the forehead. It produces a reading called BrainFlow and a score called Entropy. Temple raised $54 million in a round Goyal led, at a valuation of about $190 million. The ₹85,000 pre-order turned a debate about his research into a question for buyers.

2. Where did the idea come from?

Goyal’s Continue Research proposed that the lifelong effort of supplying blood to the brain against gravity while upright might contribute to ageing. It calls this the Gravity-Ageing Hypothesis and acknowledges that it has no direct empirical proof. A wearable that tracks short-term circulation changes would still leave the long-term ageing claim to be tested.

3. What is the Liver Doc’s objection?

Hepatologist Cyriac Abby Philips argues that a sensor over the temple can pick up the pulse and circulation in superficial vessels. His question is how much of that signal tells you what is happening inside the skull. He called the product a scam and urged regulators to examine its claims. Goyal disputes that characterisation.

4. What did Temple’s BrainFlow studies actually find?

In one preprint, the index moved with blood-flow velocity measured by ultrasound in 23 healthy adults during cycling and a posture change. A second study, funded and conducted by Temple, examined 44 healthy young men. During two of three posture tests, the index tracked the estimated brain signal more closely than the scalp signal. Both studies tested short-term changes under controlled conditions. They leave open how accurately BrainFlow tracks brain circulation in everyday use.

5. What is Entropy, and why is it a separate question?

Temple says its 1–250 score reflects how hard the body works to shed heat. Its website says the resting score reflects demands across several systems, including digestion and immunity. Goyal now calls Entropy the product’s main feature and says its supporting research is yet to be published. The two BrainFlow studies tested a different metric.

6. How has Goyal defended the price and the claims?

He says Temple is a fitness and AI device and has yet to be proven to diagnose or prevent disease. In his Diwali response, he said he expects India to account for no more than 1% of sales, invited sceptical buyers to wait for reviews and peer-reviewed evidence, and promised a fuller explanation of how BrainFlow is calculated.

7. What would settle the dispute?

An independent team would need to test whether BrainFlow can reliably distinguish changes in brain circulation from changes at the scalp across a wider range of people and activities. Entropy needs its own evidence showing what makes the score rise or fall and what a change means for the wearer. Those are separate tests for the two readings Temple is selling.