Many weight-loss efforts focus on the number on the scale, but long-term metabolic health may also depend on where fat is lost. A new study examined whether losing visceral fat, the fat stored around abdominal organs, was linked to lasting metabolic health after structured lifestyle programs.

The analysis included 381 adults with excess abdominal fat or abnormal blood lipid levels from two earlier 18-month randomized diet and physical activity trials. Long-term follow-up data were available for 366 participants. Of these, 325 returned for in-person assessments conducted 5 years after one trial and 10 years after the other trial ended. The original programs compared several dietary strategies, including Mediterranean-style approaches, and incorporated structured physical activity. Researchers used magnetic resonance imaging (MRI) scans to measure visceral fat, subcutaneous fat (fat beneath the skin), and fat in the liver and pancreas. They also measured waist size, body weight, blood markers of metabolic health, and tracked new diagnoses of type 2 diabetes through health records. These assessments also included markers of insulin resistance, which reflects how well the body responds to insulin, and metabolic syndrome severity, which combines risk factors such as excess waist size, high blood pressure, elevated blood sugar, high triglycerides, and low high-density lipoprotein (HDL) cholesterol.

• Weight returned, but waist size stayed slightly lower. Average body weight fell from about 202 to 195 pounds during the intervention and returned to about 202 pounds over the next 5 to 10 years. Waist size fell from about 42.4 to 40.3 inches and was still about 40.7 inches years later.
• Abdominal and subcutaneous fat remained lower despite weight regain. The deeper layer of subcutaneous fat decreased from 242.1 to 185.1 cm² during the intervention and measured 211.5 cm² years later. The more superficial layer fell from 132.2 to 106.1 cm² and later measured 117.6 cm², while visceral fat declined from 148.6 to 109.0 cm² and was 124.8 cm² at the long-term follow-up. Liver and pancreas fat did not stay reduced.
• Reductions in visceral fat during the intervention were linked to more favorable markers of insulin resistance and metabolic syndrome severity.
• Only visceral fat loss showed a clear diabetes risk signal. Among participants without type 2 diabetes by the end of the trials, each 10% reduction in visceral fat during the interventions was linked to a 28% lower risk of developing type 2 diabetes during follow-up.

Visceral fat is not just passive storage. When this fat depot expands, it can become more metabolically active and inflammatory. This can increase the release of fatty acids and chemical signals that can reach the liver and other organs where they interfere with the body's response to insulin. In the liver, this can weaken insulin's normal ability to restrain glucose output while also favoring greater fat production, fat release into the bloodstream, and fat storage within the liver. These shifts are closely tied to insulin resistance, abnormal blood lipids, metabolic syndrome, and diabetes. For that reason, reducing visceral fat may improve metabolic health in ways that changes in body weight alone can miss.

A key limitation is that this long-term analysis was observational, so it cannot prove that visceral fat loss itself caused the lower diabetes risk. The cohort was also more than 90% male, which limits how confidently the findings apply to women. Even so, the results suggest that some benefits of lifestyle programs may persist through changes in fat distribution even when body weight returns. In Aliquot #147, I explain how to break the visceral fat cycle.

Getting enough sleep is a central part of sleep advice, but the day-to-day consistency of sleep and wake times may also matter for long-term health. To test that idea, a study examined whether sleep regularity is linked to the risk of premature death.

The study analyzed data from more than 60,000 UK Biobank participants who were about 63 years old on average and wore an activity tracker for one week. Using those records, researchers calculated a sleep regularity score, estimating how often participants were asleep or awake at similar times from one day to the next, and compared it with average sleep length. They then linked those sleep measures to death records for up to nearly 8 years.

• Sleep regularity was a stronger predictor of death rates from any cause over the study period than average sleep length.
• Compared with the least-regular sleepers, the groups with more regular sleep patterns had about 20% to 30% lower rates of death from any cause during follow-up, after the researchers accounted for demographic, lifestyle, social, and health factors.
• The two most regular sleep groups also had about 23% to 24% lower rates of death from cancer and about 31% to 38% lower rates of death from cardiovascular, diabetes-related, and other metabolic causes.
• As a practical anchor, the researchers noted that the most regular sleepers usually fell asleep and woke within about one-hour windows, compared with about three-hour windows in the least-regular group.

Sleep timing may matter because it helps organize many of the body's daily rhythms, not just sleep itself. When bedtimes and wake times shift from day to day, the timing of light exposure, meals, physical activity, and rest often shifts with them. These cues help synchronize the body's 24-hour rhythms across many organs and tissues, including rhythms involved in blood pressure, blood sugar control, inflammation, hormone signaling, and cellular repair. Irregular timing could therefore create a kind of repeated internal mismatch, where different systems are receiving less consistent signals that help coordinate the body's daily functions.

The study was observational, so it cannot determine whether irregular sleep timing contributed to higher death rates or simply reflected underlying health problems that increased the likelihood of both irregular sleep and earlier death. Nevertheless, the findings suggest that steady sleep and wake windows deserve attention alongside getting enough sleep each night. In episode #107, Dr. Michael Grandner and I explore treatment options for insomnia and science-backed strategies for better sleep.

Increasing workout intensity can stimulate muscle cells to build and improve their mitochondria, but exercise scientists are also looking for ways to strengthen that adaptation without making workouts harder. A new study tested whether blood flow restriction (BFR), a technique that temporarily reduces blood flow to the limbs, could amplify the muscle's adaptation to sprint training.

The study included 20 healthy, physically active men with at least one year of cycling experience, who were divided into two groups with similar starting fitness levels. Both groups completed the same six-week training program, attending two supervised sessions each week. The program progressed from four to seven 30-second all-out cycling sprints per session, with 4.5 minutes of recovery between sprints. In the BFR group, pressure cuffs were wrapped around the upper thighs and inflated to 120 mmHg for two minutes after each sprint. The comparison group rested without cuffs. Muscle biopsies were used to study the participants' mitochondria, the structures inside cells that produce most of the body's energy. The researchers measured an enzyme marker of mitochondrial content and several markers of mitochondrial respiration, which estimates how well mitochondria can use oxygen to support energy production. They also assessed several measures of cycling performance, including peak oxygen use, aerobic power, sprint power, and lactate threshold measures.

• The BFR group showed a greater increase in the mitochondrial content marker over six weeks: Citrate synthase activity rose by about 12%, while it did not clearly change in the sprint-only group.
• In 12 participants with detailed mitochondrial testing, two of six mitochondrial respiration measures increased more with BFR over six weeks. They rose by roughly 70% to 80% in the BFR group, while they did not clearly increase with sprint training alone.
• Despite the mitochondrial changes, the BFR group did not clearly outperform the sprint-only group on the cycling performance measures.

All-out sprints create a large energy demand in the leg muscles, causing temporary metabolic stress and lower oxygen availability. These signals help drive training adaptations. Using BFR during recovery may prolong or intensify some low-oxygen, high-stress signals without adding more sprint work. Over time, this may strengthen cellular signals linked to mitochondrial remodeling, helping muscle fibers improve their ability to use oxygen and produce energy. However, these muscle-level changes do not always guarantee better exercise performance.

The study was small and did not randomly assign participants, so matching the groups by fitness could not rule out other differences that may have influenced the results. Even so, the findings suggest that adding BFR after sprint intervals may strengthen some muscle adaptations without changing the workout itself. In this clip, Dr. Brad Schoenfeld describes how blood flow restriction is used, its advantages, and possible drawbacks.