Serum/Plasma Lipids and Lipoproteins

Sixty-five RCT articles were evaluated for the effect of weight loss on serum/plasma concentrations of total cholesterol, low-density lipoprotein cholesterol, very low-density lipoprotein cholesterol, triglycerides, and high-density lipoprotein cholesterol. In 52 of these trials weight loss was induced by various lifestyle modifications, including diet modification and increased physical activity (356, 365, 367-370, 373, 380, 384, 399-406, 412, 431, 433, 434, 440, 446, 447, 469, 470, 473, 475, 484, 490, 677-679, 681, 683-685, 688-690, 693, 694, 700-709).

Thirteen RCT articles were reviewed that considered the effects of pharmacological therapy on weight loss and subsequent changes in total serum cholesterol level (386, 390-393, 395, 407, 408, 696-698, 710, 711).

Lifestyle Trials

Of the 52 lifestyle trials:

• 27 RCT articles examined the effect on plasma lipids of weight loss induced by diet alone, i.e., these studies simply included a diet intervention without a formal physical activity program or medications (356, 368-370, 373, 399, 400, 402, 412, 431, 433, 440, 484, 490, 677, 679, 683, 688-690, 693, 701, 702, 704, 706, 708, 709).
• 11 RCT articles examined weight loss induced by increased physical activity alone (365, 401, 404, 406, 447, 678, 685, 700, 703, 705, 707); and
• 14 RCT articles considered the combination of caloric restriction and physical activity (367, 380, 384, 403, 405, 434, 446, 469, 470, 473, 475, 681, 684, 694). 

Of the 52 lifestyle trials reviewed, 14 met the criteria for inclusion (365, 368, 370, 373, 380, 384, 399-406). The remaining 38 were not considered because:

• The no-treatment control group also lost weight (434, 446, 469, 470, 473, 475, 484, 490, 677-679, 683, 684, 688, 690, 693, 694, 701, 705, 706, 708, 709).
• There was no appropriate control group (431, 700);
• There was no difference in weight loss between the treatment and control group  (447, 702, 703);
• The dropout rate was more than 35 percent (685);
• The population was not overweight (689, 690);
• The results were not reported according to randomized treatment (681);
• The outcome measures were not reported separately for the overweight and not overweight groups (440);
• There was no measure of at least one lipoprotein fraction or measure of change in lipids between the beginning and end of treatment (356, 367, 412, 433, 704); or
• Lipoprotein concentrations could not be determined from the figures in the paper (707), or it was difficult to get precise measures (369).

Pharmacotherapy Trials

The effects of pharmacological therapy on weight loss and subsequent changes in total serum cholesterol levels were evaluated by examining 13 RCT articles: 5 on the effect of dexfenfluramine (386, 390- 393); 2 on fluoxetine (408, 711); 1 on the combination of phentermine and fenfluramine (phen/fen) (395); 2 on orlistat (407, 710); 1 on testosterone decanoate (698); 1 on ephedrine alone or in combination with caffeine (697); and 1 on a beta adrenoreceptor agonist (696). Of the 13 pharmacotherapy trials reviewed, 8 were accepted and 5 were not considered for these reasons:

• The main outcome of the treatment was not weight loss (698);
• The drug in question is not currently being recommended for weight loss (696-698);
• The dropout rate was more than 35 percent (711); or
• It was a marginal 12-week study (710).