Assessing the evidence for weight loss strategies in people with and without type 2 diabetes

Table 1 Weight loss diets in people without diabetes

Type of diet	Type of summary document	Effect size	Long term data	Recommendation	Risk markers
Low fat diet	Systematic review[18]	10% reduction in fat lowers weight by 5 kg
Low fat diet	Meta-analysis[19]	Not different to high fat weight loss diets Worth 5 kg compared with control
Low fat diet	Cochrane[20] meta-analysis 32 RCT, 54000 participants At least 6-mo duration	Mean reduction 1.5 kg for low fat without intention to lose weight	No reduction with time	High quality evidence-effect seen in almost all studies
Conclusion				A useful strategy well worth pursuing
High protein diet	Meta-analysis of 12 m or greater weight loss studies 3492 individuals[22]	SMD 0.14 for weight P = 0.008) and 0.22 for fat mass, P < 0.001 for 2%-5% energy differences in protein. > 5% energy protein difference 0.9 kg weight loss	Data out to 5 yr still shows a small residual effect		Lower triglyceride (SMD 0.17, P = 0.003) and lower insulin (SMD 0.22, P = 0.042)
High protein diet	Meta-analysis of controlled short term studies[24]	0.79 kg weight 95%CI: -1.50, -0.08 kg), 0.8 kg greater fat mass loss (-0.87 kg; 95%CI: -1.26, 0.48 ), 0.43 kg (95%CI: 0.09, 0.78) reduction in lean loss			Lower triglyceride (-0.23 mmol/L; 95%CI: -0.33, -0.12 mmol/L). Reductions in falls in REE (595.5 kJ/d; 95%CI: 67.0, 1124.1 kJ/d)
Conclusion				Small effects. Difficult to maintain a higher protein intake long term as other sources of calories creep in
Very low carbohydrate diets	Energy controlled < 45% CHO vs < 30% fat 23 trials 2788 participants[31]	Weight outcomes same			Slightly lower LDL, TG, increased HDL
Very low carbohydrate diets	Meta-analysis of 6 mo studies, 11 studies[25]	Atkins diet better by WMD -2.17 kg; 95%CI: -3.36, -0.99	Not long term	No long term benefit, possible adverse CVD effects	Triglyceride was lowered WMD -0.26 mmol/L; 95%CI: -0.37, -0.15 by the low carbohydrate diet; LDL elevated by WMD 0.16 mmol/L; 95%CI: 0.003, 0.33). HDL elevated WMD 0.14 mmol/L; 95%CI: 0.09, 0.19
Very low carbohydrate diets	Meta-analysis of 12 mo or > studies, n = 5[25]	Weight outcomes same		No long term benefit
Conclusion				No long term benefit
Very low calorie diet	Review of 12 studies[35] of VLCD vs behavioural program and diet change	VLCD was worth an additional 3.9 kg at 12 m and 1.4 kg at 24 m and 1.3 kg at 38-60 m. Dropouts were the same at 19%-20% which was lower than expected	Long term benefit seen	Worth trying with weight loss maintenance programs
Very low calorie diet	Single hospital based clinic n = 1109[36]	19% still attending at 3 yr and the mean weight loss of this group was 6.4 kg. Weight loss was 7.7% vs 2.3% for drugs (topiramate plus phentermine or sibutramine) compared with no drugs
Conclusion				Well worth trying if large weight loss required
Weight maintenance after VLCD	8 European centres[38] 11% weight loss with VLCD after 8 wk Randomised to high or normal protein 25% vs 13% and high or low GI 15U different	Fewer participants in the high-protein and the low glycemic-index groups than in the low-protein–high-glycemic-index group dropped out of the study (26.4% and 25.6% vs 37.4%; P = 0.02 and P = 0.01)	The difference in weight regain after 1 yr[39] between protein groups was 2.0 (0.4, 3.6) kg (P = 0.017) (completers analysis, n = 139) or 2.8 (1.4, 4.1) kg (P < 0.001) (intention-to-treat analysis, n = 256)	In the shop centres (where food was provided) protein had a more powerful effect (2.7 kg compared with low protein, P < 0.001) while low GI had less effect (0.48 kg, NS) Protein may have modest long term weight maintenance effects
Weight maintenance after VLCD	189 participants on VLCD for 3 mo then high or normal protein for 12 mo[40]	No difference between diets Weight regain over 9 mo was modest at 2 kg with a final weight loss of 14.5 kg overall. Overall dropout rate was 53% and compliance measures to the high protein diet were limited		Because compliance measures were limited conclusions on benefit (or absence of benefit) are limited
Conclusions				Protein may be of some benefit, GI isn’t long term. More trials required
Intermittent energy restriction	2 d partial fast and 5 normal days or alternate day fasting	Weight loss similar to CER over 3-6 mo[40-42,44,45]	No long term data		No additional metabolic benefit[47,48]
Conclusion				Insufficient data, no long term data. More work required
Glycemic index	23 young adults[50] low GI ad lib vs Low fat diet with energy reduction of 250-500 kcal	Weight loss 7.8% vs 6.1% (NS)			Triglyceride was lowered by 37.2% and 19.1% (P = 0.005) at 6 mo with no difference at 12 mo. PAI-1 was lowered by 39% with the low GI diet vs a 33% rise (despite the weight loss)
Glycemic index	73 young adults low gIycemic load diet vs low fat diet[51]	No difference at 6, 12, 18 mo Insulin above the median (57.5 μIU/mL; n = 28) at 30 min of OGTT -5.8 vs -1.2 kg on low GL diet vs low fat diet (P = 0.004) and body fat percentage (-2.6% vs -0.9%; P = 0.03). No difference in insulin sensitive group			CVD risk markers the same
Conclusion				Insufficient data for any conclusions
Mediterranean diet	Mediterranean vs low fat vs low carbohydrate diet in 322 people in a workplace setting[51]	Weight loss in the 272 completers was 2.9 kg for the low-fat group, 4.4 kg for the Mediterranean-diet group, and 4.7 kg for the low-carbohydrate group; a moderate reduction only (P < 0.001 for the interaction between diet group and time)	During 6 follow-up period, participants had regained 2.7 kg of weight lost in the low-fat group, 1.4 kg in the Mediterranean group, and 4.1 kg in the low-carbohydrate group (P = 0.004 for all comparisons) For the entire 6-yr period, the total weight loss was 0.6 kg in the low-fat group, 3.1 kg in the Mediterranean group, and 1.7 kg in the low-carbohydrate group (P = 0.01 for all comparisons) with the Mediterranean group and the low-carbohydrate group not different from each other (P = 0.22)[52]
Conclusion				Mediterranean diet best long term and has the longest follow up along with VLCD
Low sugar diet	Meta-analysis of 30 trials and 38 cohorts[53]	Adults decrease in body weight (0.80 kg, 95%CI: 0.39 to 1.21; P < 0.001) Cohort studies sugar caused increase weight increase of 0.75 kg, 95%CI: 0.30 to 1.19; P = 0.001) Interventions in children SSB vs control beverage 1 kg (95%CI for the difference, -1.54 to -0.48)[54]	12 mo difference in weight of 1.9 kg SSB vs water disappeared 12 mo after trial stopped[55]
Conclusion				Strong evidence for the benefit of sugar reduction in beverages
Multicomponent	33 RCTS of at least 1 yr’s duration[56]	Weight loss vs exercise 3.2 kg, 95%CI: -4.8 kg to -1.6 kg) Type of diet not important	Low-fat diets, some with meal replacements, with physical activity and behavior change training gave most effective long-term weight change in men (-5.2 kg after 4 yr)
Multicomponent	Commercial weight loss programs[57]	Pooled results from five study arms in commercial weight management programs showed significant weight loss at 12 mo (-2.22 kg, 95%CI: -2.90 to -1.54) Two commercial weight loss arms (mean difference -6.83 kg, 95%CI: -8.39 to -5.26) GP interventions mean difference -0.45 kg, 95%CI: -1.34 to 0.43)
Conclusion				Commercial plans of some value
Calcium	Meta-analysis of calcium RCTs	RCTs of about 600 overweight and obese individuals from 7 trials dietary calcium supplementation of about 1000 mg was associated with weight loss and fat loss of approximately 1 kg over 6 mo and had a greater effect in pre - than in postmenopausal women[59]	Calcium (1000 mg) and vitamin D after 3 yr of follow-up women with daily calcium intakes of < 1200 mg at baseline on supplements were 11% less likely to experience weight gain[61]
Conclusion				Marginal effect only
Dairy	Meta-analysis of 27 trials of dairy added to energy restriction[62] Meta-analysis of added calcium or dairy without weight restriction-no effects seen[60]	A greater reduction in body weight [-1.16 kg (95%CI: -1.66 to -0.66), P < 0.001, I² = 11%, QR = high, n = 644) and body fat mass [-1.49 kg (95%CI: -2.06 to -0.92), P < 0.001, I² = 21%, n = 521, QR = high) smaller loss of lean mass of 0.36 kg (0.01, 0.71 kg), P = 0.04, I² = 64%, n = 651, QR = moderate)	No long term data
Conclusion				Dairy may be useful component of a weight loss diet but does nothing by itself in the absence of weight loss

CER: Continuous energy restriction; CHO: Carbohydrate; GI: Glycemic index; PAI-1: Plasminogen activator inhibitor-1; QR: Quality rating; RCT: Randomised control trial; SMD: Standardized mean difference; VLCD: Very low calorie diet; WMD: Weight mean difference.

Table 2 Weight loss diets in people with type 2 diabetes

Type of diet	Type of summary document	Effect size	Long term data	Recommendation	Risk markers
Low glycemic index/low glycemic load	Canadian Trial of Carbohydrate in Diabetes[63] 12 mo study in 162 volunteers The HGI, LGI and LC diets contained 47% ± 1%, 52% ± 1% and 40% ± 1% energy carbohydrate; 30% ± 1%, 27% ± 1% and 40% ± 1% fat with GI 64 ± 0.4, 55 ± 0.4 and 59 ± 0.4	No difference between diets	None
Low glycemic index	Canadian low glycemic index diet study[64] in 210 participants with type 2 diabetes on hypoglycemic medication	No effect on weight	None		HbA1c lower buy 0.32% on low glycemic index diet compared with high fibre diet
				No value in type 2 diabetes
All randomised diets in type 2 diabetes of 12 mo or more duration	Eleven trials[65] were identified with 6754 participants were reviewed. Eight trials compared different diets while 3 compared diets to usual care. Only two study groups reported a weight loss of ≥ 5%: A Mediterranean-style diet implemented in newly diagnosed adults with type 2 diabetes and an intensive lifestyle intervention implemented in the Look AHEAD (Action for Health in Diabetes) trial
Conclusion				Mediterranean diet best
Look ahead study	The Look Ahead Study[66] enrolled 5145, aged 45-74 yr, with BMI > 25 (> 27 if taking insulin) into a weight loss (with meal replacements if required) and exercise intervention	The Intensive lifestyle intervention produced an 8.6% weight loss at 1 yr vs 0.7% in control group	At 4 yr weight was still 5.3% lower compared with control. Weight loss of 10% or more at 8 yr in 27% of the intensive lifestyle group with 50% achieving more than 5% weight loss[70] support and education control group achieved a weight loss of 10% or more in 17% of the group with 5% or more weight loss achieved by 36%		Mean HbA1c dropped from 7.3% to 6.6% At 4 yr HbA1c-0.27% lower Post hoc analysis in the whole population (4834) over 10 yr[72] showed that those who lost at least 10% of their body weight in the first year had a 21% lower (HR 0.79, 95%CI: 0.64-0.98, P = 0.034) risk of primary outcome (death from CVD, MI, stroke, admission for angina), and a 24% reduced risk of the secondary outcome (primary plus CABG, carotid endarterectomy, stent, heart failure, PVD or total mortality) (adjusted HR 0.76, 95%CI: 0.63-0.91; P = 0.003)
Conclusion				Only non-surgical weight loss study with reduction in hard end points
Atkins diet	A 6-mo study from one group of Atkins vs calorie-reduced low GI diet in volunteers with a BMI 38, of whom 80% were women[76]	Body weight fell by 11.1 kg vs 6.9 kg, P = 0.008 58.3% (49) participants completing			HbA1c was reduced by -1.5% vs -0.5% (P = 0.03) LDL was higher in the Atkins group by 4%
Atkins diet	48w study[77] comparing an Atkins diet to a low fat diet plus orlistat in which 32% of the volunteers had type 2 diabetes (n = 46)	Weight loss 8.65% to 9.5% with no differences between groups
South Beach diet	80 volunteers completed a 12 mo very low carbohydrate diet vs an energy matched high carbohydrate diet[34,78]	9.8 and 10.1 kg at 12 mo			Hba1c changes different at 6 mo but not at 12.1% reduction
Conclusions				Low carbohydrate diets good in short term with intensive support
VLCD	Meta-analysis of 5 studies of VLCD in volunteers with diabetes or no diabetes[80]	Weekly weight loss was similar in the two groups at 0.5 to 0.6 kg/wk. Weight losses of > 15%-20% were observed in these studies
VLCD	Retrospective analysis of 355 patients with diabetes matched with nondiabetics	After 12 wk, there was significant weight loss within each group when compared with baseline (T2DM: 115.0 ± 24.4 kg vs 96.7 ± 21.4 kg, P < 0.0001; non-T2DM: 117.2 ± 25.8 kg vs 97.3 ± 22.2 kg, P < 0.0001)	No long term data available
	Total cohort comprised 204 males: 506 females, age 54.0 ± 9.1; BMI 41.6 ± 8.1; weight 116.1 ± 25.1 kg[81]	At 12 wk, weight change (-18.3 ± 7.3 kg vs -19.9 ± 7.0 kg, P = 0.012) were significantly less in the T2DM group when compared with the non-T2DM group
VLCD	40 individuals with type 2 diabetes and no control group	Weight loss of 10 kg at 1 yr after an 8 wk VLCD. Five year data from a comparison of self-selected VLCD (15) to modest caloric restriction (n = 15) showed better weight loss in the conventional diet 8.9 kg vs 4.8 kg[83] Early use of VLCD can cause remission of type 2 diabetes[84]	Long term data shows benefit	VLCD useful
Conclusion				Although expensive VLCD has long term benefits
Diet plus exercise	2 controlled studies adding aerobic or resistance exercise to significant weight loss over 12 to 16 wk[86,87]	No additional benefit of adding exercise on weight	No long term data		No additional benefit on HbA1c or any other markers
Conclusions				No added benefit

CER: Continuous energy restriction; CHO: Carbohydrate; GI: Glycemic index; VLCD: Very low calorie diet.