Does Losing Weight Increase Testosterone? What the Meta-Analyses Show

“Lose weight and your testosterone will go up” is one of the most repeated claims in men's health.

It is broadly true. It is also more specific, more measurable, and more conditional than almost anyone writing about it says — and for one group of men, the evidence points the other way.

Two meta-analyses covering more than 1,700 men have put numbers on it. Here they are.

The Short Answer

In men who are overweight or obese, losing weight raises testosterone, and how much it rises tracks how much weight comes off.

A 2024 meta-analysis of 44 studies found total testosterone increased by an average of 2.5 nmol/L after a low-calorie diet and 7.2 nmol/L after bariatric surgery. An earlier 2013 meta-analysis of 24 studies reported 2.87 and 8.73 nmol/L. The larger, more recent analysis landed in the same range as the earlier one despite including substantially more evidence.

In lean men, the pattern appears to run the other way. In the small randomised-trial literature involving normal-weight, healthy men, calorie restriction tended to lower rather than raise testosterone.

This is not a general rule about eating less. It is a specific finding about reversing obesity.

What the Two Meta-Analyses Found

The larger and more recent synthesis was published in Andrology in 2024. It pooled 44 studies covering 1,774 participants and 2,159 datasets — 19 studies of low-calorie diets, 26 of bariatric surgery, one of both.

Its results for total testosterone:

• Low-calorie diet: +2.5 nmol/L (95% CI 1.9–3.1)
• Bariatric surgery: +7.2 nmol/L (95% CI 6.0–8.4)
• Both approaches combined: +4.8 nmol/L (95% CI 3.9–5.6)

And for free testosterone — the fraction not bound to carrier proteins:

• Low-calorie diet: +19.9 pmol/L (95% CI 7.3–32.5)
• Bariatric surgery: +58.0 pmol/L (95% CI 44.3–71.7)

US laboratory reports usually give total testosterone in ng/dL rather than nmol/L. Converting approximately, 2.5 nmol/L is around 72 ng/dL and 7.2 nmol/L is around 207 ng/dL. Those conversions are ours, not the paper's.

The earlier meta-analysis, published in European Journal of Endocrinology in 2013, pooled 24 studies and reported +2.87 nmol/L (95% CI 1.68–4.07) after a low-calorie diet and +8.73 nmol/L (95% CI 6.51–10.95) after bariatric surgery.

How much weight that agreement carries. The consistency between the earlier synthesis and the larger updated one strengthens confidence in the direction and rough magnitude of the effect. But the two are not independent replications: the 2024 analysis extended its search through more recent literature while still drawing on much of the same older evidence base. Agreement between an analysis and its own update is reassuring, not confirmatory in the way two separate experiments would be.

Surgery Produces Roughly Three Times the Diet Effect

Both analyses found the same pattern: bariatric surgery was associated with a testosterone increase around three times larger than dietary restriction.

A major part of the explanation is that surgery generally produces substantially greater weight loss. The 2013 analysis identified the degree of body weight lost as the single best determinant of how much testosterone rose. The 2024 analysis found the same relationship, with larger gains in men who started with a higher BMI or a lower baseline testosterone.

What these analyses cannot do is prove that kilograms alone account for the whole gap. Bariatric surgery also produces rapid changes in insulin sensitivity, gut hormone signalling, inflammation and sex hormone-binding globulin that differ from what dietary restriction produces. Additional metabolic effects of surgery cannot be excluded from these data.

So the defensible reading is: more weight lost, more testosterone gained — measured in two settings that differ in how much weight they remove, and in other ways too.

The Pattern That Runs the Other Way in Lean Men

This is the part almost nobody reports, and it matters for anyone reading a testosterone article while already at a healthy weight.

A 2022 systematic review and meta-analysis in Nutrition Reviews examined calorie restriction and testosterone specifically. From 4,198 records screened it included seven randomised controlled trials, and separated them by the participants' starting body composition.

Its finding, in the authors' own words: significant increases in total testosterone were reported in three of four studies examining calorie restriction in overweight or obese men, while significant decreases were reported in two of three studies examining normal-weight, healthy men.

Sex hormone-binding globulin rose in all four studies that measured it, regardless of body composition.

The authors concluded that the effect of calorie restriction on testosterone depends on body composition at the start.

Read this as a signal, not a law. Seven trials is a small evidence base, and the normal-weight arm of it rests on three. What it establishes is that the direction of the effect should not be assumed to be the same in lean men — not that a calorie deficit reliably lowers testosterone in every case.

It is worth pairing with something the weight-loss meta-analyses show implicitly: the lowest average starting BMI across the 44 studies in the 2024 analysis was 26.2. There were effectively no normal-weight men in that literature at all. The evidence that weight loss raises testosterone is evidence about men with excess weight, and it should not be extended past them.

Why Excess Weight Is Thought to Suppress Testosterone

One major mechanism proposed in this literature is that obesity is associated with functional suppression of the hormonal axis regulating testosterone production — the hypothalamic-pituitary-gonadal axis — and that reducing excess fat mass lifts that suppression.

The 2013 meta-analysis found supporting changes alongside the testosterone rise: estradiol fell and gonadotropins rose, which is the pattern that suppression-then-recovery would predict.

Three honest qualifications belong here. Obesity-related testosterone suppression is described as multifactorial, involving insulin resistance, inflammatory signalling, changes in sex hormone-binding globulin, sleep-disordered breathing and other pathways — no single mechanism accounts for it. Mechanisms in this area are described more confidently in popular writing than in the source literature. And hormonal changes measured alongside weight loss do not, on their own, establish which change is driving which.

What the Research Does Not Answer

Does the increase last?

The 2024 meta-analysis had a median follow-up of 26 weeks, with an interquartile range of 12 to 52 weeks. Longer observation exists in the broader literature — one prospective cohort discussed below followed participants for 36 months — but the pooled evidence is predominantly short-term.

More specifically, the meta-analysis does not establish what happens to testosterone after substantial weight regain, and no study we located was designed to follow men through a regain phase. Claims that the benefit is “sustained over time” appear in secondary summaries of this literature; the durability question is better described as unresolved.

How much weight has to come off?

Both meta-analyses found a dose relationship — more weight lost, more testosterone gained — but neither identifies a threshold below which nothing happens or above which the effect plateaus. The studies pooled a wide range of interventions and weight changes, and no source supports a specific target presented as a rule.

Does a higher testosterone level mean better symptoms?

These analyses measured hormone concentrations. Whether a particular rise translates into a change in energy, mood, libido or erectile function is a separate question with its own, less consistent literature. Related reading: Low Libido in Men: Causes, Testosterone and Treatment Options and Can Losing Weight Improve Erectile Function? What the Trials Found.

One Small Study Worth Reading Carefully

A 2024 study in the International Journal of Obesity is often quoted for a precise-sounding figure: for each kilogram of weight lost between baseline and 36 months, total testosterone increased by 0.6% (95% CI 0.2–1.0, p = 0.002) in men.

That figure is quoted accurately. The study behind it is small: 61 adults in total, of whom 17 were men, followed across four different weight-loss approaches. It was a prospective observational cohort, not a trial — participants chose their intervention — so the per-kilogram relationship is a correlation rather than a demonstrated effect.

It is a reasonable supporting observation and a poor headline. The more striking result in the same study ran the other way: in women, each kilogram lost was associated with a 0.8% decrease in total testosterone (95% CI −1.4 to −0.3).

What a Testosterone Result Actually Means

A single low reading is not a diagnosis, and this is not a minor technicality — it is what professional guidance requires.

The American Urological Association's guideline on testosterone deficiency states that “the diagnosis of low testosterone should be made only after two total testosterone measurements are taken on separate occasions with both conducted in an early morning fashion” — a Strong Recommendation graded at the highest evidence level. It suggests a total testosterone below 300 ng/dL as a reasonable cut-off supporting the diagnosis, and states that the clinical diagnosis is made only when low levels occur together with symptoms or signs.

The Endocrine Society's guideline takes the same position, recommending diagnosis “only in men with symptoms and signs consistent with testosterone deficiency and unequivocally and consistently low serum T concentrations,” with a fasting morning measurement as the initial test and the diagnosis confirmed by repeating it.

For scale: the average increases reported above — roughly 72 ng/dL after dietary weight loss and 207 ng/dL after bariatric surgery — are group averages, not individual predictions, and where any one man sits relative to a 300 ng/dL threshold depends on where he started.

Testosterone below the reference range also has causes that have nothing to do with body weight, several of which require investigation rather than lifestyle change. No article can distinguish between them for an individual. A licensed provider can order the right tests, repeat them appropriately, and interpret them in context. Related reading: Do GLP-1 Medications Affect Your Sex Drive?

Frequently Asked Questions

Does losing weight increase testosterone?

In men who are overweight or obese, yes. A 2024 meta-analysis of 44 studies and 1,774 participants found total testosterone rose by an average of 2.5 nmol/L after a low-calorie diet and 7.2 nmol/L after bariatric surgery. An earlier meta-analysis of 24 studies found 2.87 and 8.73 nmol/L. In normal-weight men, a 2022 review of seven randomised trials found calorie restriction tended to lower testosterone instead.

How much does testosterone increase after weight loss?

The pooled averages are 2.5 nmol/L (roughly 72 ng/dL) for dietary weight loss and 7.2 nmol/L (roughly 207 ng/dL) after bariatric surgery, with a combined estimate of 4.8 nmol/L. These are group averages across studies with a median follow-up of about six months, not predictions for an individual.

Can a calorie deficit lower testosterone?

In some circumstances, yes. In the randomised-trial literature involving normal-weight, healthy men, calorie restriction was associated with decreases in total testosterone in two of three studies, while in overweight and obese men the pattern went the other way in three of four. Starting body composition appears to matter, though the evidence base is only seven trials in total.

Does losing belly fat increase testosterone?

The evidence tracks overall weight and BMI reduction, not abdominal fat as a separately targeted intervention. Studies in this literature measured total weight lost and found it the strongest determinant of the testosterone rise; none isolated abdominal fat loss on its own. There is also no way to direct fat loss to a specific area, so the practical question is the same as for weight loss generally.

Why does bariatric surgery raise testosterone more than dieting?

Most of the difference is probably that it produces more weight loss — both meta-analyses found the amount lost to be the strongest determinant of the rise. But surgery also produces rapid changes in insulin sensitivity, gut hormones and inflammation that dietary restriction does not, and these analyses cannot rule out a contribution from those.

Will losing weight raise testosterone if I am already a healthy weight?

The evidence does not support assuming so. A 2022 meta-analysis of seven randomised trials found that in normal-weight, healthy men, calorie restriction was associated with significant decreases in total testosterone in two of three studies. The weight-loss meta-analyses contain effectively no normal-weight participants — the lowest average starting BMI across 44 studies was 26.2.

How long does the increase last?

Not well established. The median follow-up in the 2024 meta-analysis was 26 weeks, and the pooled evidence is predominantly short-term. No study we located followed men through a period of weight regain to see what happened to testosterone afterwards.

How much weight do I need to lose?

No study establishes a threshold. Both meta-analyses found larger increases with larger weight losses, but neither identifies a minimum amount below which nothing happens, and no source supports a specific target presented as a rule.

Does more testosterone mean better libido or erections?

Not automatically. These studies measured hormone concentrations, not symptoms. Whether a given increase changes libido, energy or erectile function is a separate question with a less consistent evidence base, and low testosterone is only one of several possible causes of those symptoms.

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References

1. Ken-Dror G, Fluck D, Fry CH, Han TS. Meta-analysis and construction of simple-to-use nomograms for approximating testosterone levels gained from weight loss in obese men. Andrology. 2024;12(2):297–315. PMID 37345263.
2. Corona G, Rastrelli G, Monami M, et al. Body weight loss reverts obesity-associated hypogonadotropic hypogonadism: a systematic review and meta-analysis. European Journal of Endocrinology. 2013;168(6):829–843. PMID 23482592.
3. Smith SJ, Teo SYM, Lopresti AL, Heritage B, Fairchild TJ. Examining the effects of calorie restriction on testosterone concentrations in men: a systematic review and meta-analysis. Nutrition Reviews. 2022;80(5):1222–1236. PMID 34613412.
4. Brzozowska MM, Bliuc D, Mazur A, et al. Sex-differential testosterone response to long-term weight loss. International Journal of Obesity. 2024;48(10):1481–1488. PMID 39014246.
5. Mulhall JP, Trost LW, Brannigan RE, et al. Evaluation and Management of Testosterone Deficiency: AUA Guideline. Journal of Urology. 2018;200(2):423–432. PMID 29601923. Reviewed and validity confirmed 2024.
6. Bhasin S, Brito JP, Cunningham GR, et al. Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline. Journal of Clinical Endocrinology & Metabolism. 2018;103(5):1715–1744. PMID 29562364.

This article is provided for general educational purposes only and is not a substitute for individualized medical advice, diagnosis or treatment. It reports pooled averages from published research, which describe groups rather than individuals, and does not recommend any particular diet, weight target or intervention. Low testosterone has multiple possible causes and requires clinical assessment, symptoms or signs, and repeat early-morning testing before any diagnosis is made. Questions about hormone levels should be discussed with a qualified healthcare professional. AmalfiDuo Journal articles are written by AmalfiDuo Editorial and are not medically reviewed — see our Editorial Policy.