Cautionary note: Watch your sugar intake. Sugar raises insulin levels, which leads to fat storage. Not only do you gain weight, but also fat cells become active hormone factories releasing inflammatory proteins into the bloodstream.

Fat (9 calories per gram)

Fat gets a bad rap. Sure, a host of studies link fat with heart disease and stroke, but the type of fat – saturated or unsaturated – makes a difference in terms of how it functions in your body, explains dietitian Joanne Larsen, founder of dietitian.com The latest research shows that healthy fats – mainly monounsaturated and polyunsaturated fats found in olive oil, avocados, seafood and nuts like almonds and walnuts – help reduce inflammation, lubricate joints, boost immune function and stave off heart disease.

While consuming too much of any kind of fat can lead to weight gain, it's important to eat enough healthy fats to keep your joints lubricated and tissues nourished.

Cautionary note: Steer clear of saturated and trans fats. Both promote inflammation, clog arteries and amp up C-reactive protein, an indicator of inflammation in the blood – and that's bad for the heart, brain, nerves and joints. So while a gram of fat contains 9 calories whether it's from lard or salmon, the long-term effects of each are very different.

"When it comes to maintaining a healthy body weight, calories still matter," says Sandon. "The goal is to make sure those calories come from nutrient-dense foods." 

Eliminate high sugar, processed foods and anything made with refined white flour. Instead, eat a Mediterranean-style diet that focuses on brightly-colored fruits and vegetables for their antioxidants; tree nuts like walnuts, almonds and pecans for their healthy monounsaturated fats and important immune-boosting minerals; and fatty fish like salmon, albacore tuna, herring and sardines for heart-healthy omega-3s. Not only will these calories help you maintain a healthy weight, they may also help keep arthritis pain at bay.