Diet and Exercise: What the Research Says

Studies almost always lead to great discussion here on Diet Blog. We analyze, ask questions, interpret and share our own experiences. Inevitably, we find flaws in the methodology, show other studies that counter it and (let's be honest) editorialize it to suit our own belief systems.

Enter the Cochrane Collaboration - made up of a group of almost 12,000 independent scientific volunteers who sift through reams of studies and select only the most rigorously conducted ones. In perusing the studies on the site, I've selected 6 topics relating to diet, weight, exercise and supplements to help provide clarity on these various issues.

Antioxidant supplements for prevention of mortality in healthy participants and patients with various diseases

• Sixty-seven randomized trials with 232,550 participants were included
• Twenty-one trials included 164,439 healthy participants. Forty-six trials included 68111 participants with various diseases
• Overall, the antioxidant supplements had no significant effect on mortality

Exercise for overweight or obesity

• 43 studies included 3476 participants
• When compared with no treatment, exercise resulted in small weight losses across studies. Exercise combined with diet resulted in a greater weight reduction than diet alone
• Increasing exercise intensity increased the magnitude of weight loss
• Exercise as a sole weight loss intervention resulted in significant reductions in diastolic blood pressure and fasting blood glucose
• Higher intensity exercise resulted in greater reduction in fasting serum glucose than lower intensity exercise
• Exercise is associated with improved cardiovascular disease risk factors even if no weight is lost.

Low glycemic index/Load diets for overweight and obesity

• Six eligible randomised controlled trials (total of 202 participants). Interventions ranged from five weeks to six months duration with up to six months follow-up after the intervention ceased.
• The decrease in body mass, total fat mass and body mass index was significantly greater in participants receiving LGI compared to comparison diets.
• The decrease in total cholesterol was significantly greater with LGI compared to comparison diets as was the change in LDL-cholesterol
• In studies comparing free eating LGI diets to conventional restricted energy low-fat diets, participants fared as well or better on the LGI diet

Omega 3 fatty acids for prevention and treatment of cardiovascular disease

• Forty eight randomized controlled trials (36,913 participants) and 41 cohort analyses were included.
• Pooled trial results did not show a reduction in the risk of total mortality or combined cardiovascular events in those taking additional omega 3 fats
• It is not clear that dietary or supplemental omega 3 fats alter total mortality, combined cardiovascular events or cancers in people with, or at high risk of, cardiovascular disease or in the general population.

Psychological interventions for overweight or obesity

• A total of 36 studies met the inclusion criteria and were included in the review. Overall, 3495 participants were evaluated.
• The majority of studies assessed behavioural and cognitive-behavioural weight reduction strategies. Cognitive therapy, psychotherapy, relaxation therapy and hypnotherapy were assessed in a small number of studies
• Behaviour therapy was found to result in significantly greater weight reductions than placebo when assessed as a stand-alone weight loss strategy
• When behaviour therapy was combined with a diet / exercise approach and compared with diet / exercise alone, the combined intervention resulted in a greater weight reduction.
• The bulk of the evidence supports the use of behavioural and cognitive-behavioural strategies.

Stretching to prevent or reduce muscle soreness after exercise

• Of the 10 included studies, nine were carried out in laboratory settings using standardized exercise protocols and one involved post-exercise stretching in footballers.
• The pooled estimate showed that pre-exercise stretching reduced soreness one day after exercise by, on average, 0.5 points on a 100-point scale
• Post-exercise stretching reduced soreness one day after exercise by, on average, 1.0 points on a 100-point scale
• Similar effects were evident between half a day and three days after exercise.
• The evidence derived from mainly laboratory-based studies of stretching indicate that muscle stretching does not reduce delayed-onset muscle soreness in young healthy adults.

Weight Training and Strength, Function, Balance and Fibromyalgia

(I lumped a few of these collaborations together).

• Weight training is effective for improving strength, function, balance in older people and may also be effective for improving physical capacity in those suffering from fibromyalgia.

Convincing but not the Final Word

The Cochrane Collaboration is helpful in drawing conclusions based on what we know so far. That said, more and more research is needed as well as self-experimentation to find what's best for our own situation and health.

It's also important to remember that they are usually testing only one aspect of an intervention and although that intervention may not be proven useful for one particular situation, it may still hold therapeutic value. Omega-3's, antioxidants and stretching come to mind here.

Keep reading, keep questioning and keep healthy the best way you know how!

Read More

• Gillian McKeith - Guru or Fraud?
• Thinking Hard Makes You Eat More
• Overcoming Toxic Hunger: A Major Cause of Obesity
• Are Your Fat Cells Sick?
• Exercise Injuries: A Diet for Recovery

• Diet Reviews
• 35+ Support Sites
• iPod and Audio Workouts
• Exercise Ideas
• Diet Delivery Services
• Blogs & Links