Dieting attempts have become popular worldwide. Dieting, however, seems to have both positive and negative health-related consequences. So far, only a few studies have focused on the determinants of dieting in detail. This study explores the association between self-report dieting attempts and intentional weight loss (IWL) during the previous year and several demographic, lifestyle, health, and psychological factors in a cross-sectional study design using data from the representative Finnish Health 2000 Survey. The sample comprised 2147 men and 2378 women, aged 30–69. Information for potential determinants was assembled via health examinations, interviews, and questionnaires. Approximately 24% of the men and 39% of the women reported dieting attempts and 10% of the men and 15% of the women reported IWL. Dieting attempts were associated with younger age, education, BMI, formerly smoking, more favourable values in lifestyle variables, and unfavorable values in serum HDL and triglycerides, a worse sense of coherence, concerns about one’s appearance, and concerns about one’s health. Among men, diabetics and those sleeping ≤6 h a night more frequently reported dieting attempts and those with osteoarthritis reported IWL. Moreover, the gradient between BMI and dieting attempts was significantly stronger in men than in women. Men seem to attempt dieting when they have actual health-related reasons, while such reasons are not so strongly associated with dieting in women. These findings can be used for determining subpopulations with obesity and real weight-loss needs and, alternatively, subpopulations with normal weight unnecessarily attempting dieting.