There are potentially many mechanisms which can disrupt the natural balance of the body and lead to the development of low-grade inflammation. The western lifestyle, characterized by lack of exercise and a diet rich in refined foods, is the most likely candidate. If chronic inflammation is indeed induced by poor lifestyle choices, the treatment is simple. Learn to make better lifestyle choices by exercising and eating healthy, nutrient-rich food! Click here to learn about available resources.
A sedentary lifestyle may contribute directly to the development of low-grade inflammation. It has been suggested that skeletal muscle acts as an endocrine organ by influencing metabolism and modifying immune system message production in other tissues including endothelial and adipose tissues.  As skeletal muscles perform work, they produce and release anti-inflammatory substances into the blood. [2, 3]
To learn more about the link between exercise and inflammation click here
Adipocytes (fat cells) may not be just guilty bystanders but may actually play a role in promoting inflammation that might lead to atherosclerosis and diabetes.  Low-grade inflammation of adipose tissue can result from chronic activation of the innate immune system.  Research has shown an association between inflammatory cytokines and proteins and adipose tissue function. [6,7] Obese individuals have higher levels of C-reactive protein.  While fatter individuals do have a greater mortality risk, it is important to note that when categorized according to level of cardiovascular fitness, weight did not matter as much as fitness level. 
Image Source: http://www.hcgobesity.org/hcg_progr/3daystest.htm
The western diet, which is loaded with refined foods, may boost inflammation especially in the cells of the blood vessel walls. The necessary nutrients for optimal immune function and prevention of cardiovascular disease and diabetes are lacking from the diet consumed by most Americans. 
Glycemic load is a predictor of type 2 diabetes independent of total calories consumed and has been shown to increase the risk of diabetes by 2.5 times in both men and women. [11,12] (Click here to learn more about the glycemic index) A study in healthy, middle-aged women showed that high glycemic loads were related to high levels of C-reactive protein, a proinflammatory marker, independent of weight and total caloric intake. 
Omega-3 fatty acids are an important substance for the functioning of the membranes of all the cells in the body. These essential fatty acids are obtained from food sources. Historically, the ratio of Omega-6 to Omega-3 fatty acids was 1:1. Now, the ratio is closer to 15:1 in westernized countries.  Polyunsaturated fatty acids, like omega-3 are associated with lower levels of proinflammatory markers (IL-6, TNF-alpha, C-reactive protein) and higher levels of anti-inflammatory markers. 
In a recent investigation of the mechanisms by which omega-3 fatty acids reduce cardiovascular mortality, blood vessel health was increased (lower levels of platelets, white blood cells, and vascular endothelial growth factor) when a Mediterranean-inspired diet was consumed for one month.  Interestingly, neither C-reactive protein nor interleukin-6 concentrations changed significantly with the Mediterranean-inspired diet. The specific interaction between Omega-3 fatty acids and the inflammatory process remains unclear. Due to the vital role that these fatty acids play in the body, their consumption is essential, regardless. Omega-3 fatty acids are found in foods such as fish, flax seeds, and nuts. They are also widely available as a nutritional supplement.
Image Source: http://www.nwri.ca/envirozine/issue43-e.html
Insufficient consumption of B vitamins and folic acid can harm the lining of blood vessels by increasing clotting, oxidative stress, and interactions with white blood cells.  Magnesium deficiency may also play a role in chronic inflammation. [18-21] Magnesium is found in foods such as whole grains, green leafy vegetables and nuts
The combination of a high meat diet and low antioxidant vitamin consumption like vitamin E and vitamin C may increase free radical production in the blood vessels and therefore increase inflammation. [22, 23]
Bacteria such as chlamydia pneumoniae are associated with inflammation and lower limb atherosclerosis. [24, 25] Helicobacter pylori, a common bacteria that effects the gastrointestinal system may cause low-grade inflammation.  Recent research indicates that herpes simplex virus may also play an important role in chronic inflammation and insulin resistance. 
Panel A shows Chlamydia pneumoniae in fibrolipid plaque from coronary artery atheroma
Image Source: http://www.cdc.gov/ncidod/EID/vol4no4/campbellG.htm