Back to Impacts

Impacts: Health impacts

Health benefits of weight loss

Last updated 16-04-2020

Even a small amount of weight loss reduces many of the adverse health effects associated with obesity. This page details the known benefits of weight loss for various medical conditions including type 2 diabetes, cardiovascular events and cancer. Lifestyle changes can also lead to improvements in many of the complications of excess weight, even if minimal weight loss occurs.

Key Evidence

01

In people with pre-diabetes, weight loss can prevent progression to type 2 diabetes

02

Moderate weight loss is beneficial for treating obstructive sleep apnoea

03

Weight loss can increase the odds of natural pregnancy in women with overweight and obesity

This page has been written by Dr Priya Sumithran and reviewed by A/Prof Samantha Hocking

Type 2 diabetes

Weight loss of 5% in insulin resistant adults with obesity improves insulin sensitivity in fat, liver and muscle, and insulin production from the pancreas,1 and these parameters improve progressively with additional weight loss. This has clinical implications for the prevention and treatment of type 2 diabetes (T2D).

Several large studies have shown that in people with pre-diabetes, weight loss of 5–7% induced by changes in diet and physical activity can reduce progression to T2D by nearly 60% over 3 to 4 years.23 Every kilogram of weight lost was associated with an estimated 16% reduction in risk of development of T2D.4

The benefits of modest weight loss extend also to people with established T2D. In a study of >5000 people with T2D, improvements in glycaemic control were seen with as little as 2–5% weight loss,5 while greater weight loss brought about progressive benefits in fasting glucose and HbA1c (a measure of average blood glucose).6 Similarly, in adults with overweight or obesity with a recent (<6 years) diagnosis of T2D, an intensive lifestyle intervention program comprising a low-energy formula diet for 3–5 months followed by stepped food reintroduction and structured support over 12 months resulted in diabetes remission at 12 months in nearly half (46%) of participants in the intervention group, compared with 4% of participants in the control group (average weight loss 10kg vs 1kg). Remission of T2D was related to the amount of weight lost, occurring in none of the participants who gained weight, and 7%, 34%, 57% and 86% of participants who lost 0–5kg, 5–10kg, 10–15kg, and more than 15kg, respectively.7 The durability of diabetes remission was linked to the extent of sustained weight loss.8

Bariatric surgery is recommended in national and international guidelines for treatment of T2D.910 A randomised study in which 150 people with obesity and T2D were treated with intensive medical therapy with or without bariatric surgery (Roux-en-Y gastric bypass [RYGB] or sleeve gastrectomy [SG]) showed that 5 years after randomisation, both types of surgery were superior to intensive medical therapy alone in achieving excellent glycaemic control and reducing the use of glucose-, lipid- and blood pressure-lowering medications.10 The beneficial effects of RYGB and SG on glycaemic control appear to be related not only to weight loss but to additional metabolic effects.11

Fatty liver disease

Improvements in fatty liver are also seen with relatively small weight losses. Imaging studies have shown that weight loss of 5% over 12 months reduces liver fat content by 33% in people with T2D, with stepwise further reductions with greater weight loss (up to 80% reduction in liver fat with >10% weight loss).12 Loss of ≥7% initial weight is associated with significant improvements in liver inflammation and injury on liver biopsy.13

Cardiovascular risk factors and events

A meta-analysis of 83 weight loss intervention studies found that any weight loss significantly reduced blood pressure and triglycerides over 2 years.14 A graded improvement with progressive weight loss is seen in these parameters, starting with as little as 2–5% weight loss (for systolic blood pressure and triglycerides) and 5–10% weight loss (diastolic blood pressure and high-density lipoprotein cholesterol).6

Although an improvement in cardiovascular risk factors is consistently shown, it is not clear whether small amounts of weight loss are sufficient to improve cardiovascular outcomes. A randomised trial of >5000 adults with T2D aged 45–76 years who were overweight or had obesity showed no difference in the occurrence of cardiovascular events over 10 years’ follow-up between people randomly assigned to an intensive lifestyle-based weight loss intervention compared with diabetes support and education.15 However, a subsequent analysis of the data suggests an association between magnitude of weight loss and cardiovascular events, as people who lost ≥10% of their body weight in the first year of the study had a 21% lower risk of cardiovascular events and mortality compared with individuals with stable weight or weight gain.16 A meta-analysis of lifestyle interventions in adults with obesity did not find a significant effect of weight loss on the development of new cardiovascular events or on cardiovascular mortality, but did demonstrate a reduction in all-cause mortality (34 trials, 685 events; risk ratio 0.82, 95% confidence interval 0.71 to 0.95) for weight loss, equating to six fewer deaths per 1000 participants.17 Another meta-analysis in patients with established coronary artery disease reported a 37% reduction in a composite outcome of all-cause mortality, cardiovascular mortality, and major adverse cardiac events with intentional weight loss.18

Although individual studies have not shown a mortality benefit with modest weight loss, a meta-analysis of randomised controlled trials involving >17,000 adults with obesity reported a 15% reduction in all-cause mortality with intentional weight loss of 5.5kg.19 Cohort studies have shown a mortality benefit with greater weight loss after bariatric surgery. For example, Swedish Obese Subjects study, in which bariatric surgery produced an average of 16–18% weight loss, found a 29% reduction in overall mortality after 10–20 years, compared with a matched unoperated control group which did not lose weight.20

Obstructive sleep apnoea

Clinical trials indicate that moderate weight loss of >10kg in people with obesity is beneficial in the treatment of obstructive sleep apnoea (OSA), with improvements in nocturnal respiratory disturbances (apnoea-hypopnoea index) and symptoms (Epworth Sleepiness Score) related to the degree of weight loss.212223

Osteoarthritis

In older adults with knee osteoarthritis, a combination of diet and exercise intervention resulting in weight loss of 5.7% produced better overall improvements in self-reported and objectively measured physical function, as well as knee pain, compared to a control group (weight loss 1.2%). Functional benefits were limited in participants who received either the diet or exercise intervention alone.24

Cancer

A meta-analysis of randomised controlled trials of various non-surgical weight loss interventions in people with obesity did not find a significant reduction in cancer incidence or mortality after modest weight loss (overall mean 3.4kg at 1 year).17 Greater weight losses may be beneficial: larger cohort studies in people with obesity have reported a decreased incidence of all cancers and obesity-related cancers in women who intentionally lost at least 9kg in adulthood,25 26 but not men,27 and meta-analyses of controlled cohort and population-based studies have demonstrated a 28–58% reduction in overall incidence of cancer, as well as specific reductions in the incidence of obesity-related cancer and breast cancer following bariatric surgery.2829

Reproductive and genito-urinary issues

In women with polycystic ovary syndrome (PCOS), lifestyle intervention reduces clinical and biochemical hyperandrogenism (excess male hormone levels), even if minimal weight loss (mean 1.7kg over 15 studies) is achieved.30 Greater weight loss after bariatric surgery has been shown to bring about a six-fold reduction in the incidence of PCOS, as well as attenuation of symptoms including menstrual irregularity and excess hair growth.31 In sub-fertile women with overweight and obesity, 4kg weight loss resulting from diet and exercise interventions improved ovulation and increased the odds of natural pregnancy, with no difference seen in assisted reproductive outcomes.32 Weight loss of 5–10% in men and women with obesity has been shown to improve urinary stress incontinence and sexual dysfunction.333435 36

Mental health and quality of life

Weight loss intervention studies have generally reported a reduction in symptoms and prevalence of depression after treatment of obesity,3738 although after bariatric surgery, particularly Roux-en-Y gastric bypass, a subgroup of patients exhibit an increased risk of depression and suicide, the cause for which has not been clearly identified. All treatments for obesity, particularly bariatric surgery, are consistently shown to be associated with an improvement in physical domains of health-related quality of life, but outcomes have been mixed for psychological aspects quality of life.39

Lifestyle intervention without weight loss

For most people, it is difficult to achieve sustained weight loss. Fortunately, lifestyle changes can lead to improvements in many of the complications of excess weight, even if minimal weight loss occurs. For example, exercise training without caloric restriction leads to improvements in endothelial function,40 visceral adiposity,41 liver fat42 and quality of life.43 In people with pre-diabetes undertaking a lifestyle intervention, although weight loss was the dominant predictor of reduced diabetes incidence, the risk of development of T2D was reduced by 44–70% in people who achieved the physical activity goal of 2.5 to 4 hours per week of moderate intensity activity, even if they did not achieve the target 5–7% weight loss.34

References

1. Magkos F et al. (2016) Effects of Moderate and Subsequent Progressive Weight Loss on Metabolic Function and Adipose Tissue Biology in Humans with Obesity. Cell Metabolism; 23:591–601
2. Knowler W et al. (2002). Reduction in the incidence of type 2 diabetes with lifestyle intervention or metformin. N Engl J Med; 346:393-403.
3. Tuomilehto J et al. (2001). Prevention of type 2 diabetes mellitus by changes in lifestyle among subjects with impaired glucose tolerance. N Engl J Med; 344:1343-50.
4. Hamman R et al. (2006). Effect of Weight Loss With Lifestyle Intervention on Risk of Diabetes. Diabetes Care; 29:2102–7
5. Look AHEAD research group. (2013). Cardiovascular Effects of Intensive Lifestyle Intervention in Type 2 Diabetes. N Engl J Med; 369:145-54
6. Wing R et al. (2011) Benefits of Modest Weight Loss in Improving Cardiovascular Risk Factors in Overweight and Obese Individuals With Type 2 Diabetes. Diabetes Care; 34:1481–6.
7. Lean M et al. (2018). Primary care-led weight management for remission of type 2 diabetes (DiRECT): an open-label, cluster-randomised trial. Lancet; 391:541–51
8. Lean M et al. (2019) Durability of a primary care-led weight-management intervention for remission of type 2 diabetes: 2-year results of the DiRECT open-label, cluster-randomised trial. Lancet Diab Endocrinol; 7:344-55
9. Australian Diabetes Society, the Australian and New Zealand Obesity Society and the Obesity Surgery Society of Australian and New Zealand 2016. The Australian Obesity Management Algorithm.
10. Rubino F et al. (2016). Metabolic Surgery in the Treatment Algorithm for Type 2 Diabetes: A Joint Statement by International Diabetes Organizations. Diabetes Care; 39:861-77
11. Schauer P et al. (2017). Bariatric surgery versus intensive medical therapy for diabetes – 5-year outcomes. N Engl J Med; 376:641-51
12. Lazo M et al, the Fatty Liver Subgroup of the Look AHEAD Research Group. (2010). Effect of a 12-month intensive lifestyle intervention on hepatic steatosis in adults with type 2 diabetes. Diabetes Care; 33:2156–63.
13. Promrat K et al. (2010). Randomized controlled trial testing the effects of weight loss on non-alcoholic steatohepatitis. Hepatology; 51:121–9
14. Zomer E et al. (2016). Interventions that cause weight loss and the impact on cardiovascular risk factors: a systematic review and meta-analysis. Obes Rev 2016;17:1001–11
15. Wing R et al. (2013). Cardiovascular effects of intensive lifestyle intervention in type 2 diabetes. N Engl J Med; 369:145-54.
16. Gregg E et al. (2016). Association of the magnitude of weight loss and changes in physical fitness with long-term cardiovascular disease outcomes in overweight or obese people with type 2 diabetes: a post-hoc analysis of the Look AHEAD randomised clinical trial. Lancet Diabetes Endocrinol; 4:913-21
17. Ma C et al. (2017). Effects of weight loss interventions for adults who are obese on mortality, cardiovascular disease, and cancer: systematic review and meta-analysis. BMJ; 359:j4849
18. Pack Q et al. (2014). The Prognostic Importance of Weight Loss in Coronary Artery Disease: A Systematic Review and Meta-Analysis. Mayo Clin Proc. 2014;89:1368–77.
19. Kritchevsky S et al. (2015). Intentional Weight Loss and All-Cause Mortality: A Meta-Analysis of Randomized Clinical Trials. PLoS ONE; 10:e0121993
20. Sjöström L. (2013). Review of the key results from the Swedish Obese Subjects (SOS) trial - a prospective controlled intervention study of bariatric surgery. J Intern Med; 273:219-34
21. Nerfeldt P et al. (2010). A two-year weight reduction program in obese sleep apnea patients. J Clin Sleep Med;6:479-86.
22. Tuomilehto H et al. (2009). Lifestyle intervention with weight reduction: first-line treatment in mild obstructive sleep apnea. Am J Respir Crit Care Med;179:3207.
23. Foster GD et al. the Sleep AHEAD Research Group of the Look AHEAD Research Group. (2009). A randomized study on the effect of weight loss on obstructive sleep apnea among obese patients with type 2 diabetes: the Sleep AHEAD study. Arch Intern Med;169:1619–26
24. Messier SP et al. (2004). Exercise and dietary weight loss in overweight and obese older adults with knee osteoarthritis. The Arthritis, Diet, and Activity Promotion Trial. Arthritis & Rheumatism; 50:1501–10.
25. Parker ED, Folsom AR. (2003). Intentional weight loss and incidence of obesity-related cancers: the Iowa Women’s Health Study. Int J Obes Relat Metab Disord; 27:1447–52.
26. Williamson D et al. (1995). Prospective study of intentional weight loss and mortality in never-smoking overweight US white women aged 40–64 years. Am J Epidemiol; 141:1128–41.
27. Williamson D et al. (1999). Prospective study of intentional weight loss and mortality in overweight white men aged 40–64 years. Am J Epidemiol; 149:491–503.
28. Casagrande D et al. (2014). Incidence of Cancer Following Bariatric Surgery: Systematic Review and Meta-analysis. Obes Surg; 24:1499–1509
29. Wiggins T et al. (2019). Cancer Risk Following Bariatric Surgery—Systematic Review and Meta-analysis of National Population-Based Cohort Studies. Obesity Surgery; 29:1031–39
30. Lim SS et al. Lifestyle changes in women with polycystic ovary syndrome. Cochrane Database of Systematic Reviews 2019, Issue 3. Art. No.: CD007506
31. Skubleny D et al. (2016). The Impact of Bariatric Surgery on Polycystic Ovary Syndrome: a Systematic Review and Meta-analysis. Obesity surgery; 26:169-76
32. Best D et al. (2017). How effective are weight-loss interventions for improving fertility in women and men who are overweight or obese? A systematic review and meta-analysis of the evidence. Human Reproduction Update; 23:681–705
33. Phelan S et al. (2012). Weight loss prevents urinary incontinence in women with type 2 diabetes: results from the Look AHEAD trial. J Urol. 2012;187:939–44.
34. Breyer BN et al, The Look AHEAD Research Group. (2014). Intensive lifestyle intervention reduces urinary incontinence in overweight/obese men with type 2 diabetes: results from the Look AHEAD trial. J Urol; 192:144-9
35. Wing R et al. (2010). Effects of weight loss intervention on erectile function in older men with type 2 diabetes in the Look AHEAD trial. Journal of Sexual Medicine; 7:156–65.
36. Wing R et al, The Sexual Dysfunction Subgroup of the Look AHEAD Research Group. (2013). Effect of intensive lifestyle intervention on sexual dysfunction in women with type 2 diabetes: results from an ancillary Look AHEAD study. Diab Care; 36:2937–44
37. Fabricatore A et al. (2011). Intentional weight loss and changes in symptoms of depression: a systematic review and meta-analysis. International journal of obesity; 35:1363-76
38. Dawes A et al. (2016). Mental Health Conditions Among Patients Seeking and Undergoing Bariatric Surgery A Meta-analysis. JAMA; 315:150-163
39. Warkentin L et al. (2014). The effect of weight loss on health-related quality of life: systematic review and meta-analysis of randomized trials. Obesity Reviews; 15:169–82.
40. Swift D et al. (2012). The effect of different doses of aerobic exercise training on endothelial function in postmenopausal women with elevated blood pressure: results from the DREW study. Br J Sports Med; 46:753-8
41. Irving B et al. (2008). Effect of exercise training intensity on abdominal visceral fat and body composition. Med Sci Sports Exerc; 40:1863-72.
42. Cassidy S et al. (2016). High intensity intermittent exercise improves cardiac structure and function and reduces liver fat in patients with type 2 diabetes: a randomised controlled trial. Diabetologia; 59:56-66
43. Martin C et al. (2009). Exercise dose and quality of life: A randomized controlled trial. Arch Intern Med; 169:269-78.