Major benchmarks saw extreme volatility on Wednesday, moving sharply lower in the morning before climbing back upward later in the session. Investors are concerned about the actions of central banks around the world, as governments appear to be competing against each other in the zero-sum game of relative global monetary policy. Yet even with macroeconomic pressure holding the market back, some individual stocks were able to post big gains. Kroger (NYSE:KR), Weight Watchers International (NASDAQ:WW), and Guardant Health (NASDAQ:GH) were among the top performers. Here's why they did so well.

Kroger gets traders' attention

Shares of Kroger picked up 7% after the grocery store giant attracted the notice of options trader Pete Najarian. The commentator noted that two different buyers are looking at Kroger, and that brought in a host of traders seeking to profit from the move in the stock. Kroger has had some difficulties so far this year; competition in the grocery industry has become ever fiercer as e-commerce players come into the field. Yet the company has a huge presence in food retail, and investors today seem optimistic that Kroger will be able to demonstrate its value either by growing its core business or by attracting the interest of someone seeking to make a bigger strategic move in the grocery industry.

Shopping cart in middle of store aisle.

Image source: Getty Images.

Weight Watchers gets closer to its goals

Weight Watchers International saw its stock jump nearly 43% following its second-quarter financial report. The wellness and weight-loss specialist said its subscriber count reached 4.6 million by the end of June, and earnings were strong enough to prompt Weight Watchers to increase its guidance for the full 2019 fiscal year. The company hasn't figured out all of its problems, as revenue sagged from year-ago levels and net income was also lower. However, investors increasingly believe that the wellness giant has started a turnaround, and efforts from Oprah Winfrey could continue to have a positive impact on Weight Watchers well into the future.

Guardant gets its health back

Finally, shares of Guardant Health closed higher by 21%. The oncological blood test specialist said that its revenue came close to tripling in the second quarter of 2019 compared to the year-earlier period, as the company saw big increases in sales of its test products both to clinical and biopharmaceutical customers. Moreover, Guardant sees those gains continuing, with expectations that full-year 2019 sales will double from 2018 levels. With so many avenues for getting even broader adoption, Guardant has a lot of potential catalysts for growth going forward.