Thursday was another quiet day on Wall Street, as major market benchmarks once again fell back slightly from their recent record run. The Dow remained less than 100 points away from the much-heralded 20,000 level, but the S&P 500 and Nasdaq Composite both fell more sharply, with losses of 0.25% to 0.5%. Investors appear to be treading water in advance of the mid-January inauguration of President-elect Donald Trump, who will face high expectations to get his pro-business policies enacted quickly and without surprises.

Despite the quiet trading day, some companies had good news, and Weight Watchers International (NASDAQ:WW), Sunoco (NYSE:SUN), and Icahn Enterprises (NASDAQ:IEP) were among the best performers in the market. Below, we'll look more closely at these stocks to tell you why they did so well.

Image source: Weight Watchers.

Oprah tips the scales at Weight Watchers

Weight Watchers International rose 5% in the wake of news that spokesperson and shareholder Oprah Winfrey had lost 40 pounds using the company's Beyond the Scale program. Weight Watchers used the celebrity's experience to launch a new promotional campaign, billed "Live Fully," which is timed to coincide with the usual New Year's rush to make resolutions for personal growth and improvement.

New television advertisements will promote the service, with Winfrey featured in three different spots that will include both her story and those of Weight Watchers' clients. Past pops for Weight Watchers stock related to Winfrey have generally been followed by longer periods of stagnant performance, but investors are nevertheless optimistic that this time will be different for the weight-loss specialist.

Sunoco gets more energetic

Sunoco climbed 13% after announcing late Wednesday that it had made some changes to its arrangements with lenders to give it more flexibility with its borrowing capacity. The master limited partnership made amendments to its revolving credit facility and term loan agreement, allowing for an increase to its permissible maximum leverage ratio and related changes to its minimum interest coverage ratio.

The amended credit facilities cover a total of $3.5 billion in potential debt, and the amendments should make it easier for Sunoco to generate enough cash to pay down debt naturally. In addition, an analyst upgrade from FBR from market perform to outperform showed the general positive attitude toward the MLP, and investors hope that the moves will mean that Sunoco won't have to reduce its distribution and income yield.

Icahn gets a Trump win

Finally, Icahn Enterprises gained 8%. Carl Icahn's limited partnership got a boost from news Wednesday that the activist investor had been named as a special advisor to the Trump administration. His focus will be on helping to deal with the state of regulation over U.S. businesses.

Icahn has worked with the President-elect on numerous occasions in the past, and most commentators see him as being particularly critical of government regulators in the Environmental Protection Agency. The activist investor hasn't hidden his anti-regulatory stance in the slightest, and it's apparent that investors believe that his ability to drive policy should be of help to Icahn's investing strategies, as well.