Why Deepinder Goyal's Temple is drawing social media scrutiny

Eternal founder Deepinder Goyal's wearable device Temple is navigating a social media storm, as doctors demand to know its scientific basis while Goyal defends his product as a fitness tracker and wellness product.

The bean-shaped gadget, worn close to one's temple, is claimed to track signals associated with brain activity and blood flow. It also claims to detects patterns such as auto chewing detection, snoring patterns and sleep patterns. Priced at ₹85,000, Temple is not yet available to the public, although the company has opened pre-orders. For now, the device is being used by a select group of early users, including investors and people associated with Goyal.

"We are not a medical device. If at some point we clinically validate any of our metrics, we will let you know," said a 5 November X post from Goyal, who has raised investments of $54 million for Temple, including from InfoEdge Ventures, Peak XV, Vijay Shekhar Sharma and Varun Alagh.

Mint spoke with medical experts, early users of the device and lawyers to understand the controversy.

Vikram Chopra, co-founder of Cars24 and an angel investor in Temple, has been using the device for two months. Chopra said the accompanying app displays several metrics similar to those offered by other fitness wearables, including sleep quality and resting heart rate.

"I use Polar, which is considered the gold standard, especially during exercise. It is a chest strap used by athletes around the world. Temple compares very well with it. I also use Whoop, a screenless, wrist-worn fitness tracker," he said.

In a post on X on 1 November, Goyal claimed that Temple recorded more accurate heart-rate readings than Whoop, Fitbit and Oura Ring in an internal study.

Scepticism

Doctors question whether a sensor placed near the temple can accurately measure blood circulation inside the brain.

"Temple appears to be measuring blood flow in the superficial temporal artery, which supplies blood to the scalp, not the brain. The brain receives blood through the internal carotid and vertebral arteries. These are not the same. Blood flow through the superficial temporal artery does not necessarily reflect blood flow inside the brain," said Dr. Kapil Singhal, director of neurology at the Institute of Neurosciences, Medanta, Noida.

One contentious claim relates to Entropy, which Goyal describes as a new biomarker tracked by Temple, measuring the body's real-time energy expenditure, or the metabolic cost of keeping the body alive.

Doctors and other experts have questioned the scientific basis of the metric, particularly as users are encouraged to lower their Entropy scores for a longer life. They argue that health and longevity recommendations should not be based on a metric that has not been independently validated.

Eternal did not respond to Mint's queries.

“I am excited about the new understanding of the human body that an instrument like this will unlock for humanity. We have a number of new research breakthroughs coming up (especially Entropy), and are validating them as we speak,” Goyal wrote on X on 6 November.

"Independent validation is important to establish what actually works and what does not. We cannot simply glorify something that may not work, but neither should we dismiss it without examining it," said Dr. Ponniah Vanamoorthy, head and senior consultant, neuroanesthesiology & neurocritical care, Kauvery Hospital, Chennai.

Some have gone to the extent of calling it a gimmick. “If Temple is not a medical device, then why is Goyal addressing the medical community and seeking peer validation? It could simply be an accessory, like an iPhone that tracks your steps and other parameters. I would call it a gimmick because there are no studies to support the claims being made,” said Dr. Kadam Nagpal, senior consultant, neurology, Salubritas Medcentre.

Legal view

Meanwhile, legal experts argue that describing Temple as a fitness or wellness device is not conclusive of its regulatory classification. If Temple is intended to measure or investigate cerebral blood flow, there is an arguable basis for treating it as a medical device, since cerebral blood flow is a physiological process.

"However, measuring a physiological parameter does not automatically make a product a medical device. The determination would depend on its intended purpose, the nature of the measurements and the manufacturer's representations," said Ketan Mukhija, partner and co-head, PE and VC Practice at Kochhar & Co.

This is not the first time Goyal has faced criticism from the scientific community. In November 2025, he drew scrutiny for proposing the Gravity Ageing Hypothesis, which suggests that Earth's gravitational pull could contribute to human ageing by gradually affecting blood flow to the brain. Doctors refuted the claim, stating there is no established scientific evidence to support the proposition.

"Blood flow to the brain is slightly lower when we stand than when we lie down, and it declines with age. Lower brain blood flow is also associated with cognitive decline. But the leap is to say that decades of standing upright cause brain ageing. There is no established evidence for that. The brain tightly regulates its own blood supply, and the association with age could run the other way: an ageing brain may simply need and receive less blood," said Dr. Anshul Sadhale, founder of FreeGymAI.