I can't see a clear conclusion, unfortunately. 'Further study required' as ever. It also seems that 'resilience' to the stress of caloric restriction is key to gaining most benefit but it's not clear exactly what resilience is, and whether it's manipulable.

From the article:

Weight loss and metabolic improvements do not explain the longevity benefits of severe dietary restrictions.

Cutting calories by 40% yielded the longest longevity bump, but intermittent fasting and less severe calorie restriction also increased average lifespan. The dieting mice also displayed favourable metabolic changes, such as reductions in body fat and blood sugar levels.

However, the effects of dietary restriction on metabolism and lifespan didn’t always change in lockstep. To the authors’ surprise, the mice that lost the most weight on a calorie-limited diet tended to die younger than did animals that lost relatively modest amounts.

This suggests that processes beyond simple metabolic regulation drive how the body responds to limited-calorie regimes. What mattered most for lengthening lifespan were traits related to immune health and red-blood-cell function. Also key was overall resilience [...] The most-resilient animals lost the least weight, maintained immune function and lived longer.

In one of the most comprehensive clinical trials of a low-calorie diet in healthy, non-obese individuals, researchers found that the intervention helped to dial down metabolic rates — a short-term effect thought to signal longer-term benefits for lifespan.

But the mouse data from Churchill’s team suggest that metabolic measurements might reflect ‘healthspan’ — the period of life spent free from chronic disease and disability — but that other metrics are needed to say whether such ‘anti-ageing’ strategies can truly extend life.