Objective: To determine the extent to which coaching over the telephone is an effective method in promoting the loss of body weight and body fat percentage. Research Methods and Procedures: Over a period of four months, in a randomized, double blind, placebo-controlled study, 120 overweight and obese (BMI 25-35 kg/m²) adults either received telephone coaching or no coaching. In addition, each participant was randomly assigned to take a supplement or placebo daily. Body weight and body fat percentage were measured at baseline, two months, and four months. Body weight was measured on an electronic scale and body fat percentage was assessed using dual energy x-ray absorptiometry (DEXA). Participants in the coaching group each received a minimum of 10 coaching sessions, each at least one week apart. Age, gender, and supplement use were controlled statistically using partial correlation. Results: When using repeated measures ANOVA, telephone coaching had a significant and favorable effect on body weight loss over the three time periods when compared to participants who received no coaching (F = 3.9, p = 0.0216). Also, when weight changes from baseline to four months were compared, ignoring the two-month time period, those in the coaching group lost significantly more weight than their counterparts (F = 4.75, p = 0.0315). When weight changes from baseline were compared to the halfway mark (two months), telephone coaching resulted in significantly greater weight loss at the trend level (F = 3.42, p = 0.0671). However, during the second half of the study (two months compared to four months), the effect of coaching was weaker and non-significant. Controlling statistically for age, gender, and supplement use, individually and collectively, had no effect on the impact coaching had on body weight loss. Telephone coaching did not play a significant role in helping participants lose body fat percentage across the three time periods compared to those who received no coaching (F = 1.28, p = 0.2797). Similarly, baseline body fat percentage means contrasted with four-month means (F = 1.65, p = 0.2018) were not significant, and findings from the two halves of the study showed that telephone coaching did not have a significant effect on the loss of body fat percentage. Discussion: Telephone coaching is an effective and inexpensive method of helping overweight and obese adults lose body weight, but not body fat percentage, over a four-month period.