Born in Charlotte, North Carolina to Indian immigrant parents from Punjab, India, Hari first attended the University of Georgia before transferring to University of North Carolina at Charlotte. After graduating in 2001 with a degree in computer science, she worked as a management consultant for Accenture. In her early 20s Hari was hospitalized with appendicitis. In response, she began looking into health and nutrition issues. She started the Food Babe blog in 2011, and left Accenture in 2012 to devote her time to activism and blogging, as well as marketing dietary and other products. By 2014, her blog was receiving over 54 million views. Hari has over 97,000 Twitter followers, and an official Facebook page with over one million likes. She refers to her followers and supporters as the “Food Babe Army.”

In 2011, Hari wrote a piece about ingredients in Chick-fil-A sandwiches which she alleged to be harmful. Chick-fil-A responded to Hari’s post in May 2012, inviting her to its headquarters in Atlanta to discuss her concerns. As part of a larger effort to improve the nutrition of their products, Chick-fil-A announced in late 2013 it was removing dyes, corn syrup, and TBHQ from their products. They also announced a plan to only use antibiotic-free chickens within the next five years.

In 2012, Hari wrote a blog post regarding Chipotle describing her quest to get clear answers about what Chipotle used in their food, saying: “Most of their food was contaminated with genetically modified cooking oil, corn oil, and they were using genetically modified ingredients in their tortillas. Even in the black beans there was GMO soybean oil. You couldn’t even order vegetarian and avoid it. It was really unfortunate. Then, when I saw their flour tortillas’ package, it said that they use trans-fat. That’s crazy.” After she published her blog post, Chipotle set up a meeting with Hari where she urged them to publish their ingredients publicly. In March 2013, Chipotle’s Communications Director emailed Hari with a link to a new page on Chipotle’s website with the ingredients in all of their menu items, along with a statement on the sidebar, “Our goal is to eliminate GMOs from Chipotle’s ingredients, and we’re working hard to meet this challenge.” In April 2015, Chipotle followed up on their commitment to remove GMO ingredients from their food and became the first national restaurant chain to use only non-GMO ingredients.

In March 2013, Hari posted her first petition on Change.org asking Kraft Foods to remove FD&C yellow#5 and FD&C yellow#6 food dyes from their Mac & Cheese. On April 1, 2013, Hari visited Kraft headquarters in Chicago bringing along over 270,000 signed petitions and met with executives. Following Hari’s visit, Kraft told ABC News Chicago they have “no plans to change the recipe for the original mac and cheese,” and “…the safety and quality of our products is our highest priority and we take consumer concerns very seriously. We carefully follow the laws and regulations in the countries where our products are sold.” Hari replied, “People have tried to petition the FDA over and over and it hasn’t worked. The best way to create change is to hold the food companies responsible.” While the dyes are legal in the U.S., Kraft uses a different formula in the United Kingdom without artificial dyes. By the end of October 2013 the petition had received about 348,000 signatures. In October 2013, Kraft announced they would change the ingredients in three of its Mac & Cheese products aimed at children, which included the use of whole grains, reduction in salt and some fats, and changing the coloring; Kraft said that the changes were not a response to the petition but rather were part of an ongoing effort to improve the nutrition of the offerings, which takes several years to plan and implement. Hari claimed credit for the changes. In April 2015, Kraft further announced that they will remove artificial dyes and artificial preservatives from all of its Mac & Cheese products by 2016.

In 2013, Hari wrote about the use of class IV caramel color in Newcastle Brown Ale on her blog and put public pressure on them to drop this ingredient. In January 2015, Heineken announced that they will stop adding class IV caramel color to their Newcastle Brown Ale, and will instead color it naturally with the same roasted malt they had previously used. Heineken’s announcement came just prior to the release of her book, The Food Babe Way (February 10, 2015), that devotes a chapter to the ingredients—including caramel coloring—in some beers, wines, and liquors.

In February 2014, Hari launched a petition on her website asking Subway to remove azodicarbonamide (a safe flour bleaching agent and dough conditioner) from their sandwich bread. The petition gathered more than 50,000 signatures in 24 hours. Subway later announced a plan to remove the ingredient from all of their sandwich breads, a process which began before her campaign. The Center For Science In The Public Interest, who advocates for its reduction, credited Hari for drawing attention to it. The Environmental Working Group supported the removal of azodicarbonamide and urged against its use. Food science experts have pointed out that the level of azodicarbonamide permitted by the FDA for use in bread is too low to pose a significant risk.

In June 2014, Hari posted a petition asking major brewers to list the ingredients in their products, something which U.S. brewers are not required to do. As part of this campaign, she claimed that commercial brewers “even use fish swim bladders” in their beer, as an undisclosed ingredient. NPR cited this as an example of fearmongering and lack of subject matter knowledge, as isinglass, derived from fish swim bladders, has been used as a natural fining agent in food and drink for centuries, and is in any case used primarily in cask ale, not vat-brewed beers, which are normally cleared by filtering. The day after she posted her petition, Anheuser-Busch and MillerCoors released ingredients in many of their products. The trade publication Beer Marketer’s Insights called Hari’s petition an “attempt of fear-mongering in the name of advocacy.” Hari later claimed that she was aware of the historic use of isinglass, and was raising attention to it for the benefit of uninformed vegans and vegetarians. In October 2015 Guinness announced that they are stopping the use of isinglass in their refining process so that their beer will become vegan-friendly.

In August 2014, Hari wrote a blog post in which she claimed there is a lack of transparency when it comes to the ingredients in Starbucks’ drinks. She noted that Starbucks doesn’t publish their ingredients online and pointed out the use of class IV caramel color and the lack of real pumpkin in Starbucks’s Pumpkin Spice Latte. This blog post received over 10 million views in 2014, and in the fall of 2015 Starbucks debuted a reformulated Pumpkin Spice Latte with real pumpkin and without caramel color. Hari took credit for this change, claiming to have emailed them monthly for updates.

Her petition about Kraft’s ingredients received over 365,000 signatures, and her Subway petition received over 50,000 signatures in the first 24 hours. Her site had a reported 52 million visitors in 2014 and over 3 million unique visitors per month.

Cheryl Wischhover, a freelance Beauty/Health/Fitness writer in Elle described Hari’s tactics as “manipulative”, “sneaky”, and “polarizing rather than productive.” Wischhover also wrote about cases of Hari deleting and failing to acknowledge past articles, and stated “The fact that she tried to ‘disappear’ these stories makes me distrust and discredit anything else she has to say, and it’s mindboggling that others still take her seriously.” In December 2014, a National Public Radio article compared her activism to fear mongering. A 2015 Slate article described her writings as using “malicious metonymy” to be deceptive. Referring to the whole food movement, Marion Nestle, professor of nutrition, food studies, and public health at New York University, says Hari “gives the movement a bad name” and prefers Hari focus on more important issues.

On February 5, 2015 Hari launched a petition on her website asking General Mills and Kellogg’s to remove the preservative butylated hydroxytoluene (BHT) from their cereals. The additive has been widely used in cereal packaging in the U.S. for many years. BHT has to be listed as an ingredient on food labels, and some consumer-protection advocates like the Environmental Working Group have advised people to avoid it when possible. Cereals marketed in Europe by General Mills and Kellogg’s do not contain the additive. Hari’s petition received over 30,000 signatures in 24 hours. On February 5, 2015, General Mills released a statement that they are removing BHT from its cereal, stating, “This change is not for safety reasons, but because we think consumers will embrace it. We’ve never spoken with Vani Hari and she did not play any role in our decision,” and “…our removal of BHT from cereals is well underway and has been for more than a year.”

In August 2015, Hari campaigned Subway in conjunction with Natural Resources Defense Council, Friends of the Earth, the Center for Food Safety, and the U.S. Public Interest Research Group to commit to buying meat produced without the routine use of antibiotics and to provide a timeline for doing so. In October 2015, Subway announced they would transition to chicken raised without antibiotics in 2016 and turkey within the following 2–3 years, and would also transition beef and pork raised without antibiotics by 2025.

In March 2015, Time named Hari among “The 30 Most Influential People on the Internet”.

Hari has been criticized by scientists and others for promoting pseudoscience. Kevin Folta has accused Hari of being “afraid of scientific engagement”. Folta stated that while her campaigns have been driven by “honest intention”, they had the effect of spreading scientific disinformation. Chemistry professor Joseph A. Schwarcz, director of McGill University’s Office for Science and Society states Hari “has no understanding of chemistry or food science” and that “her scientific background is nonexistent”. He describes azodicarbonamide, a chemical Hari opposes the usage of, as being safe for use in food but unessential. In 2015 skeptic Brian Dunning listed FoodBabe.com as #7 on a “Top 10 Worst Anti-Science Websites” list. Following her beer campaign, David Gorski, a surgeon, stated that she was “peddling pseudoscience” by portraying the chemicals used in the making of beer as dangerous.

A 2015 article in Skeptical Inquirer details products Hari declares as having toxic ingredients while Hari promotes and receives sales commissions for products containing the same or similar ingredients. Hari’s claims of toxicity have been dismissed by experts in science and medicine as incorrect or exaggerated. Hari in the past removed a product from her site when attention was drawn to it as containing chemicals she has spoken against, a body scrub called Fresh, which contained butylated hydroxytoluene (BHT). However, Hari claims that BHT is not as toxic if applied to skin as opposed to ingested.

Hari released her second book, Feeding You Lies: How to Unravel the Food Industry’s Playbook and Reclaim Your Health, in February 2019. The book appeared on the Wall Street Journal bestseller list for the week ending February 23, 2019. The Daily Beast also listed it amongst 12 Best Selling Books Published in February 2019.