Visceral fat loss may be linked to lower diabetes risk years after weight-loss programs, even if weight is regained. Digest

When body weight returns after a weight-loss program, it can obscure whether more specific changes in body fat lasted and still matter for metabolic health. A new study asked whether changes in visceral fat, the fat stored deep around the abdominal organs, were more closely linked to long-term metabolic health than weight loss alone.

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The researchers followed mostly male participants with abdominal obesity or abnormal blood lipid levels from two earlier 18-month randomized lifestyle intervention trials designed to promote moderate weight loss through diet and physical activity. During those trials, participants underwent MRI scans that measured visceral fat, subcutaneous fat (fat under the skin), fat in the liver, and fat in the pancreas. The researchers contacted those participants about 5 or 10 years after the interventions ended to determine whether changes in these fat stores were maintained and whether they were linked to later metabolic health. Of the 381 participants with MRI data from the original trials, 366 were successfully followed, including 325 who returned for in-person assessments.

• On average, body weight was largely regained, but waist size and visceral fat remained below their starting levels. Average weight was 202.1 lb/91.7 kg at the start of the original trials, 195.1 lb/88.5 kg after 18 months, and 201.5 lb/91.4 kg years later. Waist circumference decreased from 107.6 cm to 102.4 cm before rising to 103.5 cm, while visceral fat area decreased from 148.6 cm² to 109.0 cm² before rising to 124.8 cm².
• Liver and pancreatic fat did not show the same durable pattern. Liver fat fell from 10.2% to 6.4% at 18 months but was 9.6% later. Pancreatic fat changed from 14.6% to 14.1% and then rose to 15.6%.
• Each 10% reduction in visceral fat during the intervention was linked years later to a better insulin-resistance score and a healthier cardiometabolic risk score based on waist size, blood pressure, blood sugar, insulin, triglycerides, and HDL cholesterol.
• Each 10% reduction in visceral fat during the intervention was also associated with a 28% lower risk of developing type 2 diabetes during follow-up.
  
• Changes in waist size, subcutaneous fat, liver fat, and pancreatic fat were not clearly related to new type 2 diabetes diagnoses.

Unlike most subcutaneous fat, abdominal visceral fat drains through blood vessels that deliver nutrients and signaling molecules directly to the liver. When this fat depot is enlarged or metabolically unhealthy, it may expose the liver to higher levels of free fatty acids and inflammatory signals, which can worsen insulin resistance of the liver, blood lipid control, and blood-sugar regulation. This pathway helps explain why visceral-fat loss, more than total weight loss or changes in subcutaneous fat, was most clearly linked to fewer new type 2 diabetes diagnoses in this study.

A key limitation is that this was a follow-up analysis of earlier lifestyle trials, not a trial specifically designed to test diabetes prevention. So the study can link greater visceral fat loss to fewer diabetes diagnoses, but cannot prove cause and effect. Still, the findings suggest that improvements in metabolic health may persist even when lost weight is regained, particularly when visceral fat remains lower. In Aliquot #174, I explain why visceral fat is dangerous and how to reduce it.