No, but from what I've heard from dermatologists it's pretty commonly agreed upon.
And google agrees 
http://www.skincarephysicians.com/acnenet/myths.html
http://www.sportsdoctor.com/chg/common.html
http://www.disabled-world.com/artman/publish/acnefactsfiction.shtml
According to the source that physicians use most, it's unproven that diet is a factor. I left in the other stuff in case anyone wants to read it.
External factors Cosmetics may contribute to the development of acne. Oils, greases, or dyes in hair products and cosmetic creams can exacerbate the skin lesions, while water-based products are less comedogenic [12] .
Soaps, detergents, and astringents remove sebum from the skin surface but do not alter sebum production. Repetitive mechanical trauma caused by scrubbing with these agents may worsen the disorder by promoting the development of inflammatory lesions [13] . Similarly, turtlenecks, bra straps, shoulder pads, orthopedic casts, and sports helmets may all cause acne mechanica. Thus, patients with acne should avoid occlusive clothing and refrain from rubbing their faces or picking their skin.
Environmental factors such as humidity and heavy sweating also can exacerbate acne. Chloracne is caused by exposure to halogenated hydrocarbons, including dioxin, via percutaneous contact, inhalation, or ingestion. These chemicals are found in industrial products such as cutting oils and herbicides, in chemical warfare, and in contaminated food products. Clinically, chloracne is characterized by large monomorphic comedones with evolution into severely inflammatory and scarring lesions.
Diet A potential role for diet in acne is controversial [14-16] . A study of 47,355 women in the Nurses' Health Study that used a retrospective collection of data on diet during high school found an association between acne and intake of milk [17] . The authors suggest that natural hormonal components of milk and/or other bioactive molecules in milk could exacerbate acne [17,18] .
Other studies have suggested that insulin-like growth factor (IGF) may play a role in acne [19,20] . IGF is increased by ingestion of high glycemic loads and so could potentially link diet and acne. A 12-week randomized trial that compared low and high glycemic load diets in 43 male patients with acne found a greater reduction in lesion counts with the low glycemic load diet [21] . However, the participants on that diet also lost more weight than those on the high glycemic load diet, so it is possible that the results were due to changes in weight rather than the composition of the diet.Stress Patients and medical providers commonly believe that psychological stress can exacerbate acne [22,23] . A prospective cohort study in 94 secondary school students compared acne severity and sebum production at times of high stress (midterm examinations) and low stress (summer holidays) [24] . Sebum production did not appear to be related to stress, but acne severity, as assessed by an examiner blinded to the hypothesis of the study, did appear to be associated with stress, particularly in boys.
Similarly, a study of 22 university students found that in a multivariate analysis, acne severity did appear to have some correlation with stress around the time of school examinations [25] .
