Effects of multiple cycles of weight loss and regain on the body weight regulatory system in rats

Periodic protein-restricted diets extend the lifespan of high-fat diet-induced Drosophila melanogaster males

Research has shown that sustained protein restriction can improve the effects of a high-fat diet on health and extend lifespan. However, long-term adherence to a protein-restricted diet is challenging. Therefore, we used a fly model to investigate whether periodic protein restriction (PPR) could also mitigate the potential adverse effects of a high-fat diet and extend healthy lifespan. Our study results showed that PPR reduced body weight, lipid levels, and oxidative stress induced by a high-fat diet in flies and significantly extended the healthy lifespan of male flies. Lipid metabolism and transcriptome results revealed that the common differences between the PPR group and the control group and high-fat group showed a significant decrease in palmitic acid in the PPR group; the enriched common differential pathways Toll and Imd were significantly inhibited in the PPR group. Further analysis indicated a significant positive correlation between palmitic acid levels and gene expression in the Toll and Imd pathways. This suggests that PPR effectively improves fruit fly lipid metabolism, reduces palmitic acid levels, and thereby suppresses the Toll and Imd pathways to extend the healthy lifespan of flies. Our study provides a theoretical basis for the long-term effects of PPR on health and offers a new dietary adjustment option for maintaining health in the long term.

Effects of repeated weight cycling on non-alcoholic steatohepatitis in diet-induced obese mice

Lifestyle interventions remain the treatment of choice for patients with obesity and metabolic complications, yet are difficult to maintain and often lead to cycles of weight loss and regain (weight cycling). Literature on weight cycling remains controversial and we therefore investigated the association between weight cycling and metabolic complications using preexistent obese mice. Ldlr-/-.Leiden mice received a high-fat diet (HFD) for 20 weeks to induce obesity. Subsequently, weight-cycled mice were switched between the healthy chow diet and HFD for four 2-week periods and compared to mice that received HFD for the total study period. Repeated weight cycling tended to decrease body weight and significantly reduced fat mass, whereas adipose tissue inflammation was similar relative to HFD controls. Weight cycling did not significantly affect blood glucose or plasma insulin levels yet significantly reduced plasma free fatty acid and alanine transaminase/aspartate transaminase levels. Hepatic macrovesicular steatosis was similar and microvesicular steatosis tended to be increased upon weight cycling. Weight cycling resulted in a robust decrease in hepatic inflammation compared to HFD controls while hepatic fibrosis and atherosclerosis development were not affected. These results argue against the postulate that repeated weight cycling leads to unfavorable metabolic effects, when compared to a continuous unhealthy lifestyle, and in fact revealed beneficial effects on hepatic inflammation, an important hallmark of non-alcoholic steatohepatitis.

The Physiological Effects of Weight-Cycling: A Review of Current Evidence

PURPOSE OF REVIEW

There is a common perception among the public that yo-yo dieting, defined as repeated cycles of weight loss followed by weight regain, results in accumulation of fat in the body and lower metabolic rate, thus hindering subsequent attempts to lose weight. We evaluated the effects of weight-cycling on body weight and body mass index (BMI), body composition including fat mass (FM) and lean body mass (LBM), and resting metabolic rate (RMR), by systematically reviewing existing scientific literature.

RECENT FINDINGS

Twenty-three cross-sectional and cohort studies (including subjects with a history of weight-cycling compared to those without such history) and interventional studies (evaluating physiological effects during one or more cycles of weight loss and regain) were identified, conducted in generally healthy adults across various age groups, races, and both genders, who had normal weight, overweight, or obesity. Eighteen studies investigated the association between weight-cycling and body weight or BMI, and thirteen of them found no significant association. Fifteen out of twenty studies also found no increase in FM, and none of eighteen studies found a decrease in LBM. Twelve out of fourteen studies reported no adverse changes in RMR either. The overwhelming majority of evidence suggests that weight-cycling (yo-yo effect) is not associated with any adverse effects in body weight, body composition, and metabolic rate. Accordingly, healthy individuals who struggle with overweight or obesity should not be discouraged from repeated attempts to lose the excess weight.

Changes in Macronutrients during Dieting Lead to Weight Cycling and Metabolic Complications in Mouse Model

Weight cycling is a major challenge in obesity management. Caloric restriction is known to promote this phenomenon, but the impact of macronutrient changes during dieting remains unclear. This study aimed to determine the role of macronutrient changes in weight maintenance without caloric restriction by alternating between two hypercaloric diets: a high-carbohydrate, high-fat Western diet (WD) and a low-carbohydrate, high-fat diet (LCHDF). Obesity was induced in 8-week-old C57BL/6 male mice by 10 weeks of WD feeding. Then, the mice were subjected to 12 weeks of LCHFD interspersed with WD (I-WD), 3 periods of 2-week LCHFD followed by 2 periods of 3-week WD, or 12 weeks of continuous WD (C-WD). C-WD and I-WD mice were compared to standard diet (SD) mice. In the I-WD group, each LCHFD period decreased weight gain, but mice regained weight after WD resumption. I-WD mice exhibited obesity, dyslipidemia, and glucose intolerance, similarly to the C-WD mice. I-WD mice also developed nonalcoholic steatohepatitis, associated with an increase in type-III collagen gene expression and a decrease in FGF21 protein levels, in comparison with SD. I-WD mice developed weight cycling despite maintaining a high caloric consumption, suggesting that changes in macronutrients during dieting are also a trigger of weight regain.

High-fat diet-induced elevation of body weight set point in male mice

OBJECTIVE

High-fat diets (HFD) are thought to disrupt energy homeostasis to drive overeating and obesity. However, weight loss resistance in individuals with obesity suggests that homeostasis is intact. This study aimed to reconcile this difference by systematically assessing body weight (BW) regulation under HFD.

METHODS

Male C57BL/6 N mice were fed diets with varying fat and sugar in different durations and patterns. BW and food intake were monitored.

RESULTS

BW gain was transiently accelerated by HFD (≥40%) prior to plateauing. The plateau was consistent regardless of starting age, HFD duration, or fat/sugar content. Reverting to a low-fat diet (LFD) caused transiently accelerated weight loss, which correlated with how heavy mice were before the diet relative to LFD-only controls. Chronic HFD attenuated the efficacy of single or repetitive dieting, revealing a defended BW higher than that of LFD-only controls.

CONCLUSIONS

This study suggests that dietary fat modulates the BW set point immediately upon switching from LFD to HFD. Mice defend a new elevated set point by increasing caloric intake and efficiency. This response is consistent and controlled, suggesting that hedonic mechanisms contribute to rather than disrupt energy homeostasis. An elevated floor of the BW set point after chronic HFD could explain weight loss resistance in individuals with obesity.

The impact of weight cycling on health outcomes in animal models: A systematic review and meta-analysis

The pattern of weight loss and regain, termed "weight cycling," is common in overweight individuals. It is unclear whether the well-established benefits of weight loss persist following weight regain or whether weight cycling is harmful. Human studies of weight cycling have conflicting results reflecting limitations of the observational designs of these studies. By controlling the macronutrient content of diets in animal studies, weight cycling can be studied in a highly controlled manner, thereby overcoming the limitations of human studies. We conducted a systematic review and meta-analysis of animal studies which assessed the health consequences of weight cycling. Studies were classified into those which compared weight cycling to lifelong obesity and those which compared weight cycling to later onset obesity. There were no differences in health outcomes between weight cycled animals and those with lifelong obesity, highlighting that weight regain reverses health benefits achieved by weight loss. In comparison with animals with later onset obesity, weight cycled animals had higher fasting glucose levels and more impaired glucose tolerance following weight regain. Our review of animal studies suggests that health benefits of diet-induced weight loss do not persist after weight regain and weight cycling results in adverse metabolic outcomes.

Body mass cycling and predictors of body mass regain and its impact on cardiometabolic health

Caloric restriction (CR) is the first line intervention to reduce adiposity and total body mass (BM) to improve insulin resistance and ameliorate metabolic derangements. However, the lost adipose mass is difficult to maintain reduced in the long term due to several factors including compensatory changes in orexigenic hormones, adipokine release, pro-inflammatory state, adipose tissue morphology, and resting metabolic rate as a consequence of the caloric deficit. Hence, most patients undergoing a BM reduction intervention ultimately regain the lost mass and too often additional adipose mass overtime, which is hypothesized to have increased deleterious effects chronically. In this mini-review we describe the effects of BM cycling (loss and regain) on insulin resistance and cardiometabolic health and factors that may predict BM regain in clinical studies. We also describe the factors that contribute to the chronic deleterious effects of BM cycling in rodent models of diet-induced obesity (DIO) and other metabolic defects. We conclude that most of the improvements in insulin resistance are observed after a profound loss in BM regardless of the diet and that BM cycling abrogates these beneficial effects. We also suggest that more BM cycling studies are needed in rodent models resembling the development of type 2 diabetes mellitus (T2DM) in humans.

Physiological profile regulation during weight gain and loss by ovariectomized females: importance of SIRT1 and SIRT4

Obesity in menopausal women occurs because of the systemic effects of loss of ovarian function, resulting in increased body weight and oxidative stress. Caloric restriction (CR) is essential for weight loss, since it provides benefits associated with metabolic normalization resulting from the action of sirtuins. The aim of this work was to evaluate the physiological effects of weight cycling in ovariectomized females. Females aged 2 mo (n = 8/group) were submitted to simulated surgery, ovariectomy (OVX group), and ovariectomy with weight fluctuation (WF group). In the WF group, weight cycling was performed two times, using 21 days of ad libitum commercial feed and 21 days of caloric restriction with 40% of the feed consumed by the OVX group. After 17 wk, the animals were evaluated experimentally. Weight fluctuations reduced triacylglycerol and the adipose tissue index of the WF animals, while increasing the expression of antioxidant proteins. In addition to causing fluctuations in the physiological parameters, the weight cycling led to increases of adipocyte number and serum fatty acids. These effects were reflected in increased expression of the sirtuin (SIRT) 1 and SIRT4 proteins, as well as protein complexes of the mitochondrial electron transport chain, especially in the liver and adipose tissues. The weight-cycling results suggested that mitochondrial and nuclear sirtuins were active in cellular signaling for the control of lipid metabolism, oxidative phosphorylation, and redox status. Weight cycling was able to restore the health characteristics of lean animals.