Is Yo-Yo Dieting Harmful to Your Metabolism?

Yesterday, I introduced you to Marilyn* and Catherine* – both 58 years old with class 1 obesity.

Marilyn has struggled with her weigh most of her life and has an extensive history of weight cycling; Catherine had never dieted before.

Both participated in a 12 month study of diet and exercise and lost almost the same amount of weight (12% vs. 10%) and had similar improvements in metabolic parameters.

Interestingly, however, prior to beginning the study, there were some small but significant differences between Marilyn and Catherine.

Thus, not only did Marilyn have a slightly higher BMI (33 vs. 30), she also had more body fat (48.8 vs. 46.8%) and a substantially greater waist circumference (99.8 vs. 92.6 cm).

Although their blood pressure levels were identical, Marilyn had slightly higher insulin and leptin levels and was more insulin resistant (as measured by HOMA-IR).

Interestingly, these differences were not explained by differences in caloric intake, calories from fat, cardiorespiratory fitness (VO2max) or daily steps – all of which were virtually identical between the two women.

Thus, although the weight loss response was similar, it may be worth noting that Marilyn, with her history of weight cycling, despite similar caloric intake and physical activity levels, had a slightly less favourable metabolic profile.

Whether or not this difference can be attributed to her history of weight cycling, however, is not clear, as associations do not prove causality.

As the authors note,

“…several analyses where unintentional and intentional weight loss has been clearly distinguished have failed to show an independent association between weight cycling and risk of morbidity or mortality. Moreover, the risk of future weight gain previously associated with weight cycling was recently shown to be greater among women who employ unhealthy weight control strategies rather than ones generally encouraged in most structured behavior change programs .”

Thus, it may not be an issue of whether or not you have weight cycled that matters but rather the methods employed to do so.

These findings are important given the common narrative that weight cycling may be detrimental to physical health (obviously, this study (not any studies that I am aware of) address the potential negative impact of weight cycling on mental health, including self-esteem and body-image).

Would I advise either Marilyn or Catherine to lose weight if I saw them in my office?

Both appear rather healthy (EOSS 0/1) and I would see no urgency in recommending weight loss to either of them. Nevertheless, both Marilyn and Catherine could probably benefit from improving their cardiorespiratory fitness and perhaps increasing their daily steps (both of which happened during the course of the intervention).

Thus, in summary, I concur with the authors that:

“..a history of weight cycling does not impede successful participation in lifestyle interventions or alter the benefits of diet and/or exercise on anthropometric and metabolic outcomes in women. Thus, a history of unsuccessful weight loss should not dissuade an individual from future attempts at weight loss or diminish the role of a healthy diet and regular physical activity in successful weight management.”

As for the risks of weight cycling – I guess, at least metabolically speaking, it may well harbour less risk than we previously thought – although the psychological impact of losing and regaining weight may be something that will require further study.

I’d certainly appreciate hearing from my readers regarding their experiences and thoughts on yo-yo dieting.

AMS
Edmonton, AB

*The characteristics of Marilyn and Catherine are based on the average characteristics of the non-cylcer and severe-cycler participants in this study.

Mason C, Foster-Schubert KE, Imayama I, Xiao L, Kong A, Campbell KL, Duggan CR, Wang CY, Alfano CM, Ulrich CM, Blackburn GL, & McTiernan A (2013). History of weight cycling does not impede future weight loss or metabolic improvements in postmenopausal women. Metabolism: clinical and experimental, 62 (1), 127-36 PMID: 22898251

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