Fat Tissue Doesn’t Disappear
Fat cells are stubborn. They are very flexible in size, but in number, they seem to only look one way: up. Approximately 10% of your fat cells die annually. But don’t cheer yet: they are replaced by new fat cells. Researchers from the Karolinska Institute in Sweden first measured the amount of fat cells after weight loss surgery [1]. Two years after the surgery, the participants were on average much thinner than before. However, the amount of fat cells was found to be the same as before the surgery. Then they used C14 carbon dating to determine how many of these fat cells were new. This turned out to be 10%, after which they concluded that the same percentage must have died. The number of fat cells would thus remain stable after your youth.Approximately 10% of fat cells are renewed annually at all adult ages and levels of body mass index. Neither adipocyte death nor generation rate is altered in early onset obesity, suggesting a tight regulation of fat cell number in this condition during adulthood. K.L. Spalding, Karolinska InstituteTwo years later, however, this turned out to be slightly different. When researchers looked at the difference in fat cells in the abdomen and legs. In the earlier study, only the number of fat cells in the abdominal region had been examined. This number also turned out to remain the same in the 2010 study. The number of fat cells in the legs, however, had increased [2]. Fat cells in the abdomen would (with a calorie surplus) mainly increase in size, while fat cells in the lower body would increase more in number.
Average abdominal s.c. adipocyte size increased by 0.16 ± 0.06 μg lipid per cell and correlated with relative upper-body fat gain (r = 0.74, P < 0.0001). However, lower-body fat responded to overfeeding by fat-cell hyperplasia, with adipocyte number increasing by 2.6 ± 0.9 × 10(9) cells (P < 0.01). We found no depot-differences in preadipocyte replication or apoptosis that would explain lower-body adipocyte hyperplasia and abdominal s.c. adipocyte hypertrophy. Y.D. Tchoukalova, Mayo ClinicDying fat cells are thus replaced, so the body seems to ensure that the number of fat cells does not decrease. However, at the same time, the number, locally, can increase under a calorie surplus. The main message here is that you don’t get rid of fat cells. Nice, right?
Fat Sucks
Gastric bypass surgery is often an ultimate resort to help people lose weight by reducing the amount they can eat. Even after significant weight loss following gastric bypass surgery, the number of fat cells remains the same [3]. They just get smaller. With liposuction, you take a more direct approach and remove excess fat yourself instead of letting the body burn it. You just suck it away from the places you don’t want it. “What about eating less?” Quite popular, indeed. However, a year after the procedure, in most cases, the weight has returned [4]. What’s even more annoying is that the new fat itself prefers a different location. In a 2011 study, fat that was suctioned from the hips and lower abdomen of women ended up in the upper abdomen, back of the arms, and shoulders [5]. It was unclear whether the number of fat cells had been restored or if the remaining fat cells had become larger.Fat
Tissue Makes You Eat More It’s still a hypothesis, but fat cells could possibly be the cause of you eating more after losing a lot of weight [6]. The shrunken fat cells could send signals that increase appetiteWe present the hypothesis whereby the long-term signals reflecting stored energy and short-term signals reflecting nutrient availability are derived from the cellularity characteristics of adipose tissues. These signals are received and integrated in the hypothalamus and hindbrain and an energy gap between appetite and metabolic requirements emerges and promotes a positive energy imbalance and weight regain P.S. MacLean, University of Colorado
Prevention is Better Than Cure
A few years ago, I wrote about weight gain in youth, when the number of fat cells is still increasing (not only in the lower body). In “Fed Young, Dieting Old,” I extensively discuss fat cells in youth. The main message in that article is also that prevention is better than cure.References
- Spalding KL, Arner E, Westermark PO, Bernard S, Buchholz BA, Bergmann O, Blomqvist L, Hoffstedt J, Näslund E, Britton T, Concha H, Hassan M, Rydén M, Frisén J, Arner P. Dynamics of fat cell turnover in humans. Nature. 2008 Jun 5;453(7196):783-7. doi: 10.1038/nature06902. PubMed PMID: 18454136.
- Tchoukalova YD, Votruba SB, Tchkonia T, Giorgadze N, Kirkland JL, Jensen MD. Regional differences in cellular mechanisms of adipose tissue gain with overfeeding. Proceedings of the National Academy of Sciences of the United States of America. 2010;107(42):18226-18231. doi:10.1073/pnas.1005259107.
- Hoffstedt J, Andersson DP, Eriksson Hogling D, Theorell J, Näslund E, Thorell A, Ehrlund A, Rydén M, Arner P. Long-term Protective Changes in Adipose Tissue After Gastric Bypass. Diabetes Care. 2017 Jan;40(1):77-84. doi: 10.2337/dc16-1072. PubMed PMID: 27852664.
- Seretis K, Goulis DG, Koliakos G, Demiri E. Short- and Long-Term Effects of Abdominal Lipectomy on Weight and Fat Mass in Females: a Systematic Review. Obes Surg. 2015 Oct;25(10):1950-8. doi: 10.1007/s11695-015-1797-1. Review. PubMed PMID: 26210190.
- Hernandez TL, Kittelson JM, Law CK, Ketch LL, Stob NR, Lindstrom RC, Scherzinger A, Stamm ER, Eckel RH. Fat redistribution following suction lipectomy: defense of body fat and patterns of restoration. Obesity (Silver Spring). 2011 Jul;19(7):1388-95. doi: 10.1038/oby.2011.64. PubMed PMID: 21475140
- MacLean PS, Higgins JA, Giles ED, Sherk VD, Jackman MR. The role for adipose tissue in weight regain after weight loss. Obes Rev. 2015 Feb;16 Suppl 1:45-54. doi: 10.1111/obr.12255. Review. PubMed PMID: 25614203; PubMed Central PMCID: PMC4371661.
