December 31, 2024, 4:28 pm | Read time: 4 minutes
When you have lost a few pounds, the joy is often great. But the challenge afterward is to keep the weight off. According to a study, individuals with a history of obesity find it particularly difficult not to revert to old habits. FITBOOK fitness editor Janine Riedle discusses the results.
In Germany, almost 54% of adults are obese, with people aged 45 and over being particularly affected.1 In addition to the often differing aesthetic views, obesity also has health consequences. It is often associated with diabetes mellitus, high blood pressure, heart attacks, strokes, and fatty liver disease. The solution: lose weight. However, once you have shed the excess pounds, you are still a long way from reaching your goal. You first have to keep the weight off. And this is said to be not so easy with previous obesity. A study found a possible reason why it is difficult to keep the weight off after losing it.
Overview
Analyses of Adipose Tissue
The scientists aimed to determine if the yo-yo effect following weight loss could be attributed to an obesity-specific metabolic memory. Specifically, they investigated whether fat cells can ‘remember’ their previous, larger state. The researchers used human biopsies of subcutaneous and omental adipose tissue from various studies. The samples came from people who were always of normal weight as well as from people who suffered from obesity.2 Additionally, all patients had experienced a 25 percent reduction in their BMI.
The analysis of tissue samples indicated a downregulation in signaling pathways related to metabolism and fat cell functions. This suggests that obesity causes cellular and transcriptional changes in adipose tissue that persist even after weight loss.
Studies on Mice
Following these findings, scientists conducted experiments on mice to investigate the molecular mechanisms and pathophysiological significance of this suspected metabolic memory in obesity. The animals were divided into two groups. The first group received a high-fat diet for twelve or 25 weeks, while the other group received a low-fat diet. The diet was then switched to the standard diet. This led to a normalization of weight within four to eight weeks. Differences were mainly observed in insulin sensitivity and glucose tolerance.
Changes Due to Obesity
Using a so-called snRNA-seq method, the scientists examined the tissue of the mice during obesity or normal weight and after weight loss. The lipid-associated macrophage cell count, in particular, was found to be higher in the obese mice. This number did not completely normalize even after weight loss.
Furthermore, a different number of differentially expressed genes was found – i.e., the different patterns in the quantity of gene products for cells. This change was observed after weight loss and previous obesity in different cell types, such as adipocytes (cells of adipose tissue), which was accompanied by greater transcriptional deregulation. The analyses came to the same conclusion as the studies with human samples. The weight loss caused upregulation in the adipocytes, while at the same time, adipocyte-specific metabolic pathways were downregulated.
Mechanisms
The observation that mice previously obese regained weight more rapidly when fed a high-fat diet suggests a metabolic alteration that facilitates this process. As the studies show, this is due to biological memory, which is underlined by the changes in DNA and the associated proteins. However, the epigenetic memory of the fat cells is not the only reason the formerly obese mice find it difficult to maintain their weight. The scientists suspect that a similar memory exists in brain cells, and it influences how much food is consumed.
However, does this imply that individuals with obesity may struggle indefinitely to maintain weight loss? The researchers suspect that this process could subside over time. “It is possible that maintaining a reduced or healthy body weight over a long enough period of time is enough to erase the memory,” explains Dr. Laura Hinte, lead author of the study, in a press release available to The Guardian.
According to a Study Certain Intestinal Bacteria Causes Sugar Cravings
Study Can Carbonated Water Help You Lose Weight?
Study on mice Certain forms of intermittent fasting can prolong life
Classification of the Study
“Our study suggests that one of the reasons it is so difficult to maintain body weight after initial weight loss is that fat cells remember their previous obese state and probably try to return to that state,” says Prof. Ferdinand von Meyenn, a senior author of the study at the Swiss Federal Institute of Technology in Zurich, summarizing the findings. This finding could contribute to the development of better weight management programs.
However, the study warrants a critical evaluation. Although analyses with human tissue preceded the investigations, it is unclear whether all the results obtained in the animal experiments can also be transferred to humans. Further studies of clinical origin are therefore needed to support such results further.